I am so much like you on this. I always try to take some other person with me when I am purchasing colors. My son - who hates to shop and knows if he points to a bad one that I buy he'll have to go back with me is best. But friends or anyone will do. If I need three colors, I can find two and never the third, etc. etc.
I recently made a quilt for a friend fighting cancer and took 2 friends with to pick out the fabric. I needed three each of two different colors. In less than 5 minutes the two friends had picked out all 6 and they all played nice together in the quilt. It would have taken me two hours and I would have ended up with at least 2 clunkers.