The hex color #effa3e is a light color. The web-safe version is Hex
#FFFF33. A complementary color is
#1005C1. The grayscale version is
#B8B8B8. A 20% lighter version of the original color is
#FFFF71, and Hex
#BCC70B is the 20% darker color. If the color is saturated by 10%, you get
#F5FF32. If the color is desaturated by 10%, the color
#E9F34A is obtained.