The hex color #21c81b is a light color. The web-safe version is Hex
#33CC33. A complementary color is
#DE37E4. The grayscale version is
#575757. A 20% lighter version of the original color is
#54FB4E, and Hex
#009500 is the 20% darker color. If the color is saturated by 10%, you get
#1CD315. If the color is desaturated by 10%, the color
#26BD21 is obtained.