Can be done via macro. Not as extensively as you might want, but still. Press [ESC] ingame and then click [Macro]. Click [New], choose a name and a icon.
Yes, but i also would want the spell visuals for the character.
They did Night Fae Death Knight Decay as blue color, that is what i am also after here.
I wants the same done to each spell.
For example Shadow Priest MIND FLAY could be yellow if you are Kyrian.
You would end up with mad amount of macros if you play with multiple charas.
And there would be some spells that you wouldnt be able to choose color this way anyway.
Like Warrior Leap, there are not that many icons that would resemble it.
Painting tool would be way simpler, it could be implemented into TMOG category.
It would be like chancing your saturation settings, or similar.
Or then they would need to make these icons layered with color codes.