I'm a real conservative as far as colors go, more comfortable with subtle shadings and combinations than wild and almost-clashing mixtures. In a garden, pale yellow is almost a neutral and will complement any color, pinks or oranges or gold.
Blues and purples are useful anywhere as well. But, to me, the purple-pink needs to be supported by rose, purple, blue and pale yellow. Nothing bugs me more than seeing flowering plums (light purple-pink blossoms) against a beige or yellow house. The trees just look out of place. Next to gray, cool white or blue, they shine.
And the safe colors can be used in large amounts, giving the garden a sense of continuity. Forget-me-nots are great for this, self-seeding just about everywhere.
