Fluids only use the texture to render, not the color which is added onto the fluid registeration.

Here is an example of this https://github.com/thevortex/bettercompat/blob/master/src/main/java/com/bettercompat/main/init/FluidInit.java#L99

This and all the other Base Tinkers Construct fluids use a greyscale texture shared across all the fluids and tint it using the color property. This is rendered correctly in tanks and the like, but when placed in the world to flow they only show the greyscale texture without the tint.

someone else had opened a optifine bug sp614x/optifine#5634 but i think its more likely something that optiforge can handle since it is related to forge mod fluid objects.

I've been working on a few fluids for my own work and ran into this problem, which is frustrating since if you use a colored texture you cant use a tint as that causes the fluid in the world and the fluid in the tanks to render differently.

Old Optifine bug
sp614x/optifine#3226 (comment)