Color changes at different times of the year, also from heat and intensity of sunlight. I find light pinks to be the worst culprit for having that washed out look in full summer sun. Its sort of a conundrum, you need the full sun to keep them healthy and get them to bloom a lot, but they look better when placed in part shade, the pinks hold their delicate coloring better. Thats why I enjoy light pinks most in early spring and later autumn, they look their best then to me.