Picking which colors go well together is much easier than most people think. The key to choosing the right colors for the right occasions is all about the color wheel.
A couple of basic rules: Gray
& White are neutral colors. They go with any color in the rainbow.
The most basic color match is to keep items within the same color family, but different shades. Wearing colors that are varying degrees of depth and darkness is considered a monochromatic look. This is a sophisticated and conservative look, but that is never a bad thing.
Looking at a color wheel you can see that each color has its opposite and complimentary color. Going around the circle the complimentary color is the one that is directly opposite it on the other side of the wheel. Purple is opposite yellow, blue is opposite orange, red is opposite green, etc. This is a simple complimentary color match and will always work in fashion. This also explains why light green and pink match so well.
Now looking at the color wheel, draw a balanced triangle in the color wheel and those three colors all match each other. Take for example: Blue, Yellow and Red. They form a basic color triangle that will match the colors well.