Index: cpp/frams/genetics/f4/f4_conv.cpp
===================================================================
--- cpp/frams/genetics/f4/f4_conv.cpp	(revision 1298)
+++ cpp/frams/genetics/f4/f4_conv.cpp	(revision 1313)
@@ -1,4 +1,4 @@
 // This file is a part of Framsticks SDK.  http://www.framsticks.com/
-// Copyright (C) 1999-2023  Maciej Komosinski and Szymon Ulatowski.
+// Copyright (C) 1999-2024  Maciej Komosinski and Szymon Ulatowski.
 // See LICENSE.txt for details.
 
@@ -189,5 +189,5 @@
 	}
 
-	char tmpLine[100];
+	char tmpLine[256];
 	MultiRange range = C->genoRange;
 
@@ -200,6 +200,6 @@
 			// new part object for firstend
 			// coordinates are left to be computed by Model
-			sprintf(tmpLine, "fr=%g,ing=%g,as=%g",
-				/*1.0/C->P.mass,*/ C->P.friction, C->P.ingestion, C->P.assimilation
+			sprintf(tmpLine, "fr=%g,ing=%g,as=%g,vr=%g,vg=%g,vb=%g",
+				/*1.0/C->P.mass,*/ C->P.friction, C->P.ingestion, C->P.assimilation, C->P.cred, C->P.cgreen, C->P.cblue
 				//C->firstend.x, C->firstend.y, C->firstend.z
 			);
@@ -216,7 +216,7 @@
 		}
 		// new part object for lastend
-		sprintf(tmpLine, "fr=%g,ing=%g,as=%g",
+		sprintf(tmpLine, "fr=%g,ing=%g,as=%g,vr=%g,vg=%g,vb=%g",
 			//C->lastend.x, C->lastend.y, C->lastend.z
-			/*"vol=" 1.0/C->P.mass,*/ C->P.friction, C->P.ingestion, C->P.assimilation
+			/*"vol=" 1.0/C->P.mass,*/ C->P.friction, C->P.ingestion, C->P.assimilation, C->P.cred, C->P.cgreen, C->P.cblue
 		);
 		C->p2_refno = addFromString(PartType, tmpLine, &range);
@@ -241,4 +241,5 @@
 		C->joint_refno = addFromString(JointType, tmpLine, &range);
 		if (C->joint_refno < 0) return -13;
+		getJoint(C->joint_refno)->vcolor = (getPart(jj_p1_refno)->vcolor + getPart(jj_p2_refno)->vcolor) / 2; //joint gets the average color of both connected parts
 		this->checkpoint();
 	}
Index: cpp/frams/genetics/f4/f4_general.cpp
===================================================================
--- cpp/frams/genetics/f4/f4_general.cpp	(revision 1298)
+++ cpp/frams/genetics/f4/f4_general.cpp	(revision 1313)
@@ -1,4 +1,4 @@
 // This file is a part of Framsticks SDK.  http://www.framsticks.com/
-// Copyright (C) 1999-2023  Maciej Komosinski and Szymon Ulatowski.
+// Copyright (C) 1999-2024  Maciej Komosinski and Szymon Ulatowski.
 // See LICENSE.txt for details.
 
@@ -1414,5 +1414,5 @@
 			char *ptr = (char*)(genot + pos_inout);
 			string original = "";
-			while (GenoOperators::strchrn0(all_modifiers_no_comma, *ptr)) //only processes a section of chars known in all_modifiers_no_comma, other characters will exit the loop
+			while (GenoOperators::strchr_no0(all_modifiers_no_comma, *ptr)) //only processes a section of chars known in all_modifiers_no_comma, other characters will exit the loop
 			{
 				original += *ptr;
@@ -1422,9 +1422,9 @@
 			if (advanced > 0) //found modifiers
 			{
-				string simplified = GenoOperators::simplifiedModifiers(original);
+				string simplified = GenoOperators::simplifiedModifiers(original, F14_MODIFIERS_COLOR);
 				// add a node for each char in "simplified"
 				for (size_t i = 0; i < simplified.length(); i++)
 				{
-					int pos = GenoOperators::strchrn0(genot + pos_inout, simplified[i]) - genot; //unnecessarily finding the same char, if it occurrs multiple times in simplified
+					int pos = GenoOperators::strchr_no0(genot + pos_inout, simplified[i]) - genot; //unnecessarily finding the same char, if it occurrs multiple times in simplified
 					f4_Node *node = new f4_Node(simplified[i], par, pos); //location is approximate. In the simplification process we don't trace where the origin(s) of the simplified[i] gene were. We provide 'pos' as the first occurrence of simplified[i] (for example, all 'L' will have the same location assigned, but at least this is where 'L' occurred in the genotype, so in case of any modification of a node (repair, removal, whatever... even mapping of genes) the indicated gene will be one of the responsible ones)
 					par = node;
Index: cpp/frams/genetics/f4/f4_oper.cpp
===================================================================
--- cpp/frams/genetics/f4/f4_oper.cpp	(revision 1298)
+++ cpp/frams/genetics/f4/f4_oper.cpp	(revision 1313)
@@ -1,4 +1,4 @@
 // This file is a part of Framsticks SDK.  http://www.framsticks.com/
-// Copyright (C) 1999-2023  Maciej Komosinski and Szymon Ulatowski.
+// Copyright (C) 1999-2024  Maciej Komosinski and Szymon Ulatowski.
 // See LICENSE.txt for details.
 
@@ -17,5 +17,5 @@
 // TODO add mapping genotype character ranges for neural [connections]
 // TODO The f0 genotypes for /*4*/<<RX>X>X> and RX(X,X) are identical, but if you replace R with C or Q, there are small differences (they were present both before and after the change in C,Q effects in the f1 converter in 2023-06, see conv_f1_f0_cq_influence) - check why (modifiers affecting cells=sticks are applied differently or skip some initial sticks?) and perhaps unify with f1?
-// TODO F4_SIMPLIFY_MODIFIERS in f4_general.cpp: currently it works while parsing (which is a bit "cheating": we get a phenotype that is a processed version of the genotype, thus some changes in modifiers in the genotype have no effect on its phenotype). Another (likely better) option, instead of simplifying while parsing, would be during mutations (like it is done in f1): when mutations add/modify/remove a modifier node, they could "clean" the tree by simplifying modifiers on the same subpath just as GenoOperators::simplifiedModifiers() does. This way, simplifying would be only performed when we actually modify a part of a genotype, not each time we interpret it, and there would be no hidden mechanism: all visible genes would have an expected effect on the phenotype.
+// TODO F4_SIMPLIFY_MODIFIERS in f4_general.cpp: currently it works while parsing (which is a bit "cheating": we get a phenotype that is a processed version of the genotype, thus some changes in modifiers in the genotype have no effect on its phenotype). This is especially noticeable with color modifiers, where simplification only accepts MAX_NUMBER_SAME_TYPE_COLOR. Another (likely better) option, instead of simplifying while parsing, would be during mutations (like it is done in f1): when mutations add/modify/remove a modifier node, they could "clean" the tree by simplifying modifiers on the same subpath just as GenoOperators::simplifiedModifiers() does. This way, simplifying would be only performed when we actually modify a part of a genotype, not each time we interpret it, and there would be no hidden mechanism: all visible genes would have an expected effect on the phenotype. In other words, if a genotype happened to have more modifiers of the same type than allowed by GenoOperators::simplifiedModifiers(), they would all be effective (like in f1) and not silently ignored when interpreting that genotype. For example in /*4*/GGGgGX> due to simplifying modifiers (removing the oldest), only the last G remains effective when MAX_NUMBER_SAME_TYPE_COLOR=1, and it is impossible to adjust colors precisely even by manually editing the genotype - like it is in f1, even though the same simplifying function is used, just in a different moment.
 // TODO improve the way modifiers are handled in the f4->f1 approximate converter (used extremely rarely just for illustration)
 
@@ -32,5 +32,4 @@
 
 
-const char *Geno_f4::all_modifiers = F14_MODIFIERS ","; //comma in f4 is handled the same way (simple node, F4_ADD_SIMP) as modifiers. See also all_modifiers_no_comma in f4_general.cpp.
 
 // codes that can be changed (apart from being added/deleted)
@@ -56,5 +55,5 @@
 
 	{ "f4_mut_max_rep", 1, 0, "Maximum number for '#' repetitions", "d 2 20 6", FIELD(mut_max_rep), "Maximum allowed number of repetitions for the '#' repetition gene", },
-	{ "f4_mut_exmod", 1, 0, "Excluded modifiers", "s 0 30", FIELD(excluded_modifiers), "Modifiers that will not be added nor deleted during mutation\n(all: " F14_MODIFIERS ")", },
+	{ "f4_mut_modifiers", 1, 0, "Allowed modifiers", "s 0 100", FIELD(allowed_modifiers), "Modifier symbols that will be added or deleted during mutation\n(from the full set: " F14_MODIFIERS ").\n\nYou may use the extended syntax: after every allowed symbol, you may include its probability value in parentheses.\nWithout parentheses, all allowed symbols behave as if they had (1.0) appended.\nIf you include (0.0) after a symbol, this bans that symbol as if it was not present in this string.", },
 	{ 0, },
 };
@@ -84,5 +83,5 @@
 void Geno_f4::setDefaults()
 {
-	excluded_modifiers = F14_MODIFIERS_RARE F14_MODIFIERS_VISUAL;
+	allowed_modifiers = F14_MODIFIERS_BASIC F14_MODIFIERS_COLOR_SPORADIC;
 }
 
@@ -183,5 +182,20 @@
 			f4_Node *node_new = NULL; //stick or neuron or neural connection
 			if (rndDouble(1) < STICK_OR_NEURON)
+			{
 				node_new = new f4_Node('X', node_new_div, node_new_div->pos);
+				//now add one color modifier before this new X, just as in f1's Geno_f1::addMutationColoredX()
+				if (prob[F4_ADD] > 0 && probadd[F4_ADD_SIMP] > 0) //user wants modifier mutations, so we are allowed to prepend a random color modifier to "X"
+				{
+					char color_mod = GenoOperators::getRandomColorModifier(allowed_modifiers.c_str(), F14_MODIFIERS_COLOR); //may return 0 if no color modifiers available
+					if (color_mod != 0)
+					{
+						//adding a new color modifier node just as in the F4_ADD_SIMP case later below.
+						node_new->parent->removeChild(node_new);
+						f4_Node *n2 = new f4_Node(color_mod, node_new->parent, node_new->parent->pos);
+						n2->addChild(node_new);
+						node_new->parent = n2;
+					}
+				}
+			}
 			else
 			{
@@ -220,5 +234,5 @@
 				}
 			}
-			new f4_Node('>', node_new, node_new->pos); //adds to node_new
+			new f4_Node('>', node_new, node_new->pos); //adds '>' to node_new
 			node_mutated->parent = node_new_div;
 			// now, swap children with 50% chance
@@ -294,11 +308,12 @@
 		{
 			// add simple node
-			int modifier_index = GenoOperators::getRandomChar(all_modifiers, excluded_modifiers.c_str());
-			if (modifier_index < 0)
+			SString allowed_modifiers_and_comma = allowed_modifiers + ","; // traditionally, in f4, comma was treated here equally with modifiers
+			char modifier = GenoOperators::getRandomModifier(allowed_modifiers_and_comma.c_str());
+			if (modifier == 0)
 				return GENOPER_OPFAIL;
 			node_mutated->parent->removeChild(node_mutated);
 			// old source: choose a simple node from ADD_SIMPLE_CODES
 			//f4_Node *n2 = new f4_Node(ADD_SIMPLE_CODES[rndUint(strlen(ADD_SIMPLE_CODES))], node_mutated->parent, node_mutated->parent->pos);
-			f4_Node *n2 = new f4_Node(all_modifiers[modifier_index], node_mutated->parent, node_mutated->parent->pos);
+			f4_Node *n2 = new f4_Node(modifier, node_mutated->parent, node_mutated->parent->pos);
 			n2->addChild(node_mutated);
 			node_mutated->parent = n2;
@@ -722,5 +737,11 @@
 	else if (strchr(">", ch))                style = GENSTYLE_RGBS(0, 0, 100, GENSTYLE_NONE);
 	else if (strchr(STYL4CAT_DIGIT, ch))     style = GENSTYLE_CS(GENCOLOR_NUMBER, GENSTYLE_NONE);
-	else if (strchr(STYL4CAT_MODIFIC, ch))   style = GENSTYLE_RGBS(100, 100, 100, GENSTYLE_NONE);
+	else if (strchr(STYL4CAT_MODIFIC, ch))
+	{
+		if (strchr(F14_MODIFIERS_COLOR, ch)) //color modifier - less important so less visible on white
+			style = GENSTYLE_RGBS(200, 200, 200, GENSTYLE_NONE);
+		else //non-color modifier
+			style = GENSTYLE_RGBS(100, 100, 100, GENSTYLE_NONE);
+	}
 	else if (strchr(STYL4CAT_NEUMOD, ch))    style = GENSTYLE_RGBS(0, 150, 0, GENSTYLE_NONE);
 	if (isalpha(ch))
Index: cpp/frams/genetics/f4/f4_oper.h
===================================================================
--- cpp/frams/genetics/f4/f4_oper.h	(revision 1298)
+++ cpp/frams/genetics/f4/f4_oper.h	(revision 1313)
@@ -1,4 +1,4 @@
 // This file is a part of Framsticks SDK.  http://www.framsticks.com/
-// Copyright (C) 1999-2023  Maciej Komosinski and Szymon Ulatowski.
+// Copyright (C) 1999-2024  Maciej Komosinski and Szymon Ulatowski.
 // See LICENSE.txt for details.
 
@@ -59,6 +59,5 @@
 	paInt mut_max_rep;                ///maximum allowed number of repetitions for the '#' repetition gene
 
-	SString excluded_modifiers;       ///<Modifiers that are excluded in mutation process
-	static const char *all_modifiers;
+	SString allowed_modifiers;        //to be used in mutations
 
 private:
