Thinking about this and the fact I've been buying more online this year (for so many reasons) I realize that my color-match needs have diminished in favor of more controlled scrappy projects. If it's 'in the range' of the colorway I'm going after then great - if not, it goes into stash. FYI - my current online favorite has been the Thousands of Bolts site because of their abundance of 'Shorts and FQ'.
Back to the topic of color matching online - the only way that I've been successful is to buy the same line or bundles.