The hex color #3d3f4d is a dark color. The web-safe version is Hex
#333366. A complementary color is
#C2C0B2. The grayscale version is
#434343. A 20% lighter version of the original color is
#707280, and Hex
#0A0C1A is the 20% darker color. If the color is saturated by 10%, you get
#3C3F4E. If the color is desaturated by 10%, the color
#3E3F4C is obtained.