I'd go back and complain to be honest, I know it's their job to try and get sales for commission but it's very poor representation of the company to tell you that something doesn't suit your skin type/skin colour but continue to push for the sale anyway.
I'm quite pale, with pretty much flawless skin apart from the problem of red patches. The foundations I use are Nars Sheer Glow, which is best worked in with the fingers, as brushes do absolutely nothing for this foundation which provides good coverage, although probably a little heavier than I like.
Another of my favourite foundations is the Mac Face and Body, they do a completely white version of this which you can mix in with a coloured version to make it lighter tone. A little bit of a hassle, but I picked it up from the makeup artist Charlotte Tilbury who does a lot of pale skin celebrities like Jessica Chastain.