The hex color #3d3f5f is a dark color. The web-safe version is Hex
#333366. A complementary color is
#C2C0A0. The grayscale version is
#494949. A 20% lighter version of the original color is
#707292, and Hex
#0A0C2C is the 20% darker color. If the color is saturated by 10%, you get
#3C3E61. If the color is desaturated by 10%, the color
#3E405D is obtained.