Location helps, although it helps more with some locations than others. :D

And yeah, I've gotten to the point where if I'm offered a guide with black-and-white drawings or color photos, I'll pick the drawings. It's an excellent demonstration of why we still need artists' eyes in the age of the camera! Especially with wildflowers, where there can be huge variation in color, and the photos often don't show the foliage very well. The photographic ones are more fun to just sit at home and page through, though.