I have made a lot of fabric purchases on ebay in the last few months and there is only one where the color was a little different than pictured (but I still love it) but I think that is a computer monitor issue, like TVs diferent ones can have different colors on the same show.
I do make a point of only buying fabrics like Moda, Thimbleberries, Jinny Beyer, etc. and I do watch the ratings and make sure that they have a positive feedback record