The hex color #3f587d is a dark color. The web-safe version is Hex
#336666. A complementary color is
#C0A782. The grayscale version is
#5C5C5C. A 20% lighter version of the original color is
#728BB0, and Hex
#0C254A is the 20% darker color. If the color is saturated by 10%, you get
#3C5880. If the color is desaturated by 10%, the color
#42587A is obtained.