Implement _changed() mechanism in Color, by having Colors know which items they are defining styles for, through an internal _owners list.

src/color/Color.js

@@ -270,7 +270,7 @@ var Color = this.Color = Base.extend(new function() {
 								? ((value % 360) + 360) % 360
 								// All other values are 0..1
 								: Math.min(Math.max(value, 0), 1);
-							this._cssString = null;
+							this._changed();
 							return this;
 						};
 					}, src);
@@ -306,6 +306,27 @@ var Color = this.Color = Base.extend(new function() {
 }, {
 	/** @lends Color# */
 
+	_changed: function() {
+		this._cssString = null;
+		for (var i = 0, l = this._owners && this._owners.length; i < l; i++)
+			this._owners[i]._changed(Change.STYLE);
+	},
+
+	_addOwner: function(item) {
+		if (!this._owners)
+			this._owners = [];
+		this._owners.push(item);
+	},
+
+	_removeOwner: function(item) {
+		var index = this._owners ? this._owners.indexOf(item) : -1;
+		if (index != -1) {
+			this._owners.splice(index, 1);
+			if (this._owners.length == 0)
+				delete this._owners;
+		}
+	},
+
 	/**
 	 * Returns the type of the color as a string.
 	 * 
@@ -357,7 +378,7 @@ var Color = this.Color = Base.extend(new function() {
 
 	setAlpha: function(alpha) {
 		this._alpha = alpha == null ? null : Math.min(Math.max(alpha, 0), 1);
-		this._cssString = null;
+		this._changed();
 		return this;
 	},
 

src/color/GradientColor.js

@@ -136,6 +136,7 @@ var GradientColor = this.GradientColor = Color.extend({
 		this._origin = origin;
 		if (this._destination)
 			this._radius = this._destination.getDistance(this._origin);
+		this._changed();
 		return this;
 	},
 
@@ -175,6 +176,7 @@ var GradientColor = this.GradientColor = Color.extend({
 		destination = Point.read(arguments).clone();
 		this._destination = destination;
 		this._radius = this._destination.getDistance(this._origin);
+		this._changed();
 		return this;
 	},
 
@@ -218,6 +220,7 @@ var GradientColor = this.GradientColor = Color.extend({
 		} else {
 			this._hilite = hilite;
 		}
+		this._changed();
 		return this;
 	},
 

src/item/PathStyle.js

@@ -104,6 +104,12 @@ var PathStyle = this.PathStyle = Base.extend(new function() {
 				var old = this['_' + key];
 				if (old != value && !(old && old.equals && old.equals(value))) {
 					this['_' + key] = value;
+					if (isColor) {
+						if (old)
+							old._removeOwner(this._item);
+						if (value)
+							value._addOwner(this._item);
+					}
 					if (this._item) {
 						this._item._changed(Change.STYLE
 								| (strokeFlags[key] ? Change.STROKE : 0));