White sphere, three identical materials, each with unique color: red, green, and white.
Two texture maps driving the opacity of the material labels (red and green).
As far as I can tell, there is no way to control how the colors should behave at points in which the colors overlap. For example, it would be nice to be able to select from blend modes for material labels, as is the case with the color composite node.
Is this true?
I think you are correct. You could control the opacity of each one with textures, but not blending modes.