I have no intention on getting the full ColorPicker back and running.
Copying colors to wagons was the only thing I ever used it for in the first place.
Copy Locomotive and Stop colors to cargo wagons and fluid wagons as you copy other settings between entities.
Mooncat's color mask is added only to base fluid-wagon.
Add this mod as dependency if you wish to have working colors on your fluid wagons.
deprecated for 0.18:
Please support yeahtoasts much improved fluid wagon color masks: