I'm assuming you mean the color would be assigned to the output? What would be the use case for this? Is this something you do already with other tools? Would It only be useful for subjects where there is just one local color like a sculpture? In a landscape where the blue sky and green grass are the same value, you would have to assign that value either blue or green. How would you pick?

It should be possible to select any color for each value zone, to produce what some call a "heatmap".