I assumed you do not know material editor, and tired to make it easy to duplicate (ie. no messed up things).
create RGB stripes:
stretch uvs 3 times in single direction:
combine textures:
whole graph (dirty):
Combining 3 of anything:
- assume “Zero/default” state is one of 3 options
- use option 0 for whole thing
- use 2 if statments, if something is more that other, use option 1, if something is less that other thing use option 2.
But i did RGB stripes anyway.
Whole thing would be easier if you just masked R from uv then:
set default RGB = [0,0,1]
if R < 0.33 set MAsk texture to RGB=[1,0,0]
if R > 0.67 set MASK texture to RGB=[0,1,0]
then Lerp with RGB your pieces together.
I was doing that when you wrote you can do whole thing yourself. 