Nature in Shades of Blue and Yellow

My nephew who was visiting the last week (he of the snakes) is red-green colorblind, as we say colloquially. I've not been out in the field with someone with this particular quirk of vision to such an extent before, and it was very interesting. It also pointed out how inadequate most published field guides are for people with this color vision deficiency, a situation that about 10% of males are in. We flipped through a bird guide, and some interesting observations included these:

A male Scarlet Tanager is a drab, dull, dark bird. In contrast, a female is a brilliant, brightly-colored creature. Similarly, a male Painted Bunting is a mostly drab bird with a bright blue head, while the female is much more conspicuous. The male Indgo Bunting is a brilliant blue bird (we saw some of them in person). Goldfinches jump right out with their bright colors, but male Cardinals are about as obvious as dead twigs. Yellow appears to be his "red," meaning the color that is most bold and attention grabbing. But adding a little red to a shade makes it seem dark and dull to him, much like adding black does to me. Orange colors are dull, looking much like olive green and brown. In general, he is more strongy clued in to pattern than color, in comparison to most people with ordinary three-color vision.

I suggested to him he could make a killing by launching a series of field guides for the red-green colorblind.