The hex color #66a5f4 is a light color. The web-safe version is Hex
#6699FF. A complementary color is
#995A0B. The grayscale version is
#AAAAAA. A 20% lighter version of the original color is
#99D8FF, and Hex
#3372C1 is the 20% darker color. If the color is saturated by 10%, you get
#5FA4FB. If the color is desaturated by 10%, the color
#6DA6ED is obtained.