--- a/ImageEditView.st	Thu Oct 18 00:36:02 2018 +0200
+++ b/ImageEditView.st	Sat Oct 20 11:32:19 2018 +0200
@@ -1931,11 +1931,11 @@
                         ^ self.
                     ].
                     answer == #new ifTrue:[
-                        existingColors := image usedValues asIdentitySet.
-                        newColors := copiedImage usedValues.
-                        allColors := existingColors addAll:newColors.
+                        existingColors := image usedColors asSet.
+                        newColors := copiedImage usedColors.
+                        allColors := (Set withAll:existingColors) addAll:newColors; yourself.
                         allColors size > (1 bitShift:image depth) ifTrue:[
-                            self warn:(resources string:'Sorry: too many colors - unimplemented function').
+                            self warn:(resources string:'Sorry: too many colors - please change the depth, then paste again').
                             self undo.
                             ^ self.
                         ].