The hex color #feff3d is a light color. The web-safe version is Hex
#FFFF33. A complementary color is
#0100C2. The grayscale version is
#BEBEBE. A 20% lighter version of the original color is
#FFFF70, and Hex
#CBCC0A is the 20% darker color. If the color is saturated by 10%, you get
#FFFF30. If the color is desaturated by 10%, the color
#F8F94A is obtained.