i don't think may possible change colours but may be well possible add a prefix as "_" to the menu entry to all default script and plugin (and then recompile...)
I think to "_" because that should keep them on top even if have no a reserved menu ,but i think may be any other prefix .
Edit and recompile all extra script and plugin seems much more complex almost hopeless, would be a eternal work in progress
But the other way around, compile a modified Gimp version where the default script /plugin have a added prefix is possible ...maybe a bit tedious but doable
Quote:
There was a question some time ago on one of the mailing lists about plug-ins having their own icons like the standard tools do
I fear will be a mess , may work for few, if generalized gimp will be full of the most cryptic and bizarre icons
But thinking better should be already doable, i remember a icon in the menu entries of the filters included in GIMP#