I'm confident of my colour choices because I audition my fabric on the Design Wall. I really don't care what other people think.
But if I'm making something for someone else, I do try to use colours or styles that I know they like.
There are some excellent books, sites, and pinterest colour boards for newbies. An easy trick is to find a print you love and pull colours to go with it using those handy little dots in the selvedge.