Green tinted with gray is restful and soft. Bright yellow can be warmed with oranges and earth tones such as caramel and brown, or toned down with violet. Yellow with red takes you on a trip to Provence, France. When treated as a neutral, red is warm and comforting. A spicy orange-red hints at the exotic, and blue shows off red's mysterious, dreamy side.
Deeper blues become jewel-like when complemented with reds or greens.
I like to have some symmetry.