This article talks about the options for women whose skin is darker than "medium fair", as well as all the limitations. There are also tips on using concealer that apply to those of us who don't have such a hard time finding products at the drugstore.
And the makeup artist author points out that you can have even coverage OR naturally-looking skin, but not both. So it's not that I just haven't found the right foundation that will look invisible on my skin. It doesn't exist, despite what all the blog reviews try to tell me. Time to lower the expectations, I guess. Or just stick with concealer and powder, like usual, and save myself some money.