Color theory is a body of knowledge about the visual impact of specific color combinations. Orginally conceived for painters and then modified for the printing industry, it's also useful for choosing clothing combinations.
There are three principal types of color schemes. A monochromatic scheme is comprised of different shades of one color, such as a navy blue suit, light blue shirt and mid-blue necktie with navy stripes.
An analogous color scheme is comprised of colors that are adjacent to each other on a color wheel (A color wheel is a wheel used to show the relations of colors). Tan, red, and yellow are adjacent to each other on the wheel and might be worn successfully as a tan suit, yellow shirt and red necktie.
Complementary colors are colors that are opposite each other on the color wheel, such as the orange Alexander Olch necktie worn next to a blue suit in the photo. When used side-by-side, opposites make each other appear brighter.
There's a color wheel at Wellstyled.com that's designed to produce color schemes for web pages. Playing with it for a few minutes may give you ideas that will be helpful when you're dressing in the morning.