It's a little strange to me how the combined image looks a lot more bright and colored compared to the images on the right. I assume the color comes from the cortex and medulla which absorb and scatter light which derive from when the light passes through the hair. How do these elements work together to bring out more color when they're combined in the "all" image?
I would think that since some of these share components, like TT and TTs, for example, they may look darker in the isolated images on the right, but in the combined image the darker aspects of each contribute less to the overall brighter color
I think it looks funny because it feels like many dark colors would combine to become an even darker color, but in color, "pure black" would be the zero. As long as things are slightly brighter than "pure black", adding them together gets them further from "pure black" and so makes the overall image lighter.