I was like SuzyQ, I had garment sewed for years and there you didn't mix stipes, plaid flowers etc and usually only worked with maybe two colors. It has taken a coupel of years, but I am finally expanding my color choice for quilts. Working on one now with 4 colors, a long way from where I was and I love the combo.
One thing I know I did for a long time was to look TOO CLOSE for a match. You need to do as someone else here suggested and put the fabrics on a table and step back several feet. Best to turn and walk away, then turn back and look (not stare) and the odd ball that don't belong will jump out. It seems the longer you look the harder it is to be satisfied.