I shop online and have never had an issue. In fact, recently I ordered some fabric from Over the Rainbow in Camano, WA (overrainbow.com) and she didn't have all that I wanted, so I asked her where I might get more. She actually contacted the mfr for me to see if they had any more. They didn't, but I was impressed that she did that for me. I have always had good luck with her and other shops.
I go to the several LQS around, but there is so much variety online. You just have to try and see which vendors you like. If your monitor is current and the vendor uses a decent scanner, you can get a fairly true idea of the fabric colors. Another option is go to the mfr website (if known) and look there.