You can choose complementary colors using nearly any paint company's color palette guides, while keeping in mind what colors will not be changing on your home's exterior. Nearly every manufacturer of paint provides suggestions for which of their paints will match and complement each other nicely.
While choosing the right color palette may be difficult, it is easier than trying to assemble your own palette from scratch. Important things to consider when choosing the colors you want to use are the position of sun and the light on your home, how the paint will look against your brick or stone accents, if any, or even how the paint will look in conjunction with your neighbors.
It is also important to note that depending on your neighborhood, there may be restrictions on what colors you can use on your home.
If you are intent on choosing your own unique palette, you can use the manufacturer-suggested palettes as guides. After you have seen enough of the suggested palettes, you begin to understand the philosophy behind choosing colors: neutral colors that have a hint of color combine well with bright or earthy tones, while bright colors need to be tempered by neutral tones or dark colors. Finally, never underestimate the effect that using bright white or black can provide in framing the edges.