4 Super Simple Ways to Master Color Mixing
Give it the ombré test.
Different shades of the same color or similar colors almost always look good together (yes, this includes red and pink). If you need some help, do a Google image search for "ombré [insert color here]" and see what pops up.
Try the "J.Crew Hack."
J.Crew shoots all their clothes fully styled on a model, and they have a really great way with color. Take the piece of clothing you are looking to build into an outfit, then go on JCrew.com or open one of their catalogues and find something, anything, the same color.