The hex color #3f3f5f is a dark color. The web-safe version is Hex
#333366. A complementary color is
#C0C0A0. The grayscale version is
#4A4A4A. A 20% lighter version of the original color is
#727292, and Hex
#0C0C2C is the 20% darker color. If the color is saturated by 10%, you get
#3E3E61. If the color is desaturated by 10%, the color
#40405D is obtained.