The hex color #21ecb3 is a light color. The web-safe version is Hex
#33FFCC. A complementary color is
#DE134C. The grayscale version is
#959595. A 20% lighter version of the original color is
#54FFE6, and Hex
#00B980 is the 20% darker color. If the color is saturated by 10%, you get
#15F5B6. If the color is desaturated by 10%, the color
#2DE3B0 is obtained.