The hex color #663c8f is a dark color. The web-safe version is Hex
#663399. A complementary color is
#99C370. The grayscale version is
#666666. A 20% lighter version of the original color is
#996FC2, and Hex
#33095C is the 20% darker color. If the color is saturated by 10%, you get
#663893. If the color is desaturated by 10%, the color
#66408B is obtained.