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yeee - it is most obvious to use bitmap to do such - but in my post i more mean real color modification of Water datatype - like you do from Project Settings in current 4040+ WM releases. But with usage of masks for diferent color in diferent areas
water datatype have cool animation of waves, also it not solid as heightmap in your example that uses as fundament for bitmap - water datatype is just overlay layer of water
so i did mean ability to directly change color of water datatype
but thanks for explanation, yeee 
developer also did already comment that idea: Is it possible to produce colorful water datatype? - #2 by Stephen