For your casual wardrobe, try to avoid the traditional "khaki" color, which can look, what I call, a little too suburban. Instead, opt for gray (light or dark), blue (a bright blue is great), dark jeans and navy.
For dress trousers and suits, stick with a medium to dark gray and navy. A black suit will never go out of style, but a blue suit is a bit more modern and looks fabulous with white, red, yellow, orange, lavender... you name it, you can wear it with navy!