The hex color #663a8f is a dark color. The web-safe version is Hex
#663399. A complementary color is
#99C570. The grayscale version is
#656565. A 20% lighter version of the original color is
#996DC2, and Hex
#33075C is the 20% darker color. If the color is saturated by 10%, you get
#663693. If the color is desaturated by 10%, the color
#663E8B is obtained.