The hex color #213D4B is a dark color. The web-safe version is Hex
#333333. A complementary color is
#DEC2B4. The grayscale version is
#383838. A 20% lighter version of the original color is
#54707E, and Hex
#000A18 is the 20% darker color. If the color is saturated by 10%, you get
#1F3D4D. If the color is desaturated by 10%, the color
#233D49 is obtained.