The hex color #21b5cc is a light color. The web-safe version is Hex
#33CCCC. A complementary color is
#DE4A33. The grayscale version is
#8B8B8B. A 20% lighter version of the original color is
#54E8FF, and Hex
#008299 is the 20% darker color. If the color is saturated by 10%, you get
#16B9D2. If the color is desaturated by 10%, the color
#2CB1C6 is obtained.