The hex color #51a991 is a light color. The web-safe version is Hex
#669999. A complementary color is
#AE566E. The grayscale version is
#848484. A 20% lighter version of the original color is
#84DCC4, and Hex
#1E765E is the 20% darker color. If the color is saturated by 10%, you get
#4CAD92. If the color is desaturated by 10%, the color
#56A590 is obtained.