I've seen the book of his color work. I like color photography. So much so, that I've shot nothing but color since 1983 for my personal work. I'm not anti-color or anti Ansel Adams.
The difference between a really good color photo and a black and white photo of the same subject is that when you look at the color photo and imagine it in black and white - or take a monochromatic viewing filter and look at the photo to see what it might look like in B&W - you end up saying, "no, works much better in color." In other words, the color gives an added dimension to the work that makes the photo work for that subject - and it absolutely would not work as well in B&W because of that added dimension.
That just isn't true with Ansel's color work. When I look at his color work, it's a scene that looks good (well composed, framed, etc.) but, there is no intrinsic reason that the photo has to be in color. It could be done in B&W and work just as well, or perhaps even better. They are very good photos, they just don't have the added reason that they have to be rendered in color and no other way.
I've also seen an exhibition of Edward Weston's color work. They were 8x10 Ilfochrome contact prints of the film he shot as part of an Eastman Kodak trial advertising campaign using famous photographers shooting Kodak color transparency film. Interestingly, he went back and exactly duplicated some of his black and white photos in color, others were new compositions. Although they were great compositions, they didn't have that "spark of recognition" that gives his B&W work so much life.
This may be because he was using some subjects that he had already photographed successfully in B&W, and hence the "rediscovery" in color didn't gain his full involvement, but, even the new subjects didn't have an intimate interaction of the photographer with the color aspects of the subject. This is sort of a long way of saying, "interesting, yes - photos didn't work as color photos."
To me, this is what makes color photography so difficult. It's a total involvement with seeing the subject for its color qualities and incorporating those into the photo in a way that reinforces the subject. You have to specifically find the reason for making a photo in color instead of in B&W. It's more than just finding a nice subject, setting up the camera, and loading it with color film instead of black and white. I just don't get the "total involvement with color" as part of Ansel's color work. Instead, I get the subsitution of color film for black and white with a subject.
For all those reasons, they just don't work for me at a basic level as good color photographs.