Complementary: This scheme uses two colors which are directly opposed on the color wheel (for example: Orange and Blue)
Split Complementary: This scheme uses 3 colors. One color and two other colors that are directly adjacent to its complement on the color wheel (for example: Orange, Blue-Violet, and Blue-Green)
Triad: This color scheme uses 3 colors that are equally spaced out on the color wheel (for example: Orange, Violet, and Green)
Analogous: This scheme uses three colors, one that is in the center, and the two colors adjacent to it on the color wheel (for example: Orange-Yellow, Orange, and Red-Orange).
Monochromatic: This color scheme uses colors from the same Hue on the color wheel, but with varying saturation and/or lightness (for example: different shades or tints of Orange). Jill Denton ~ Changing Spaces