The hex color #3fd811 is a light color. The web-safe version is Hex
#33CC00. A complementary color is
#C027EE. The grayscale version is
#636363. A 20% lighter version of the original color is
#72FF44, and Hex
#0CA500 is the 20% darker color. If the color is saturated by 10%, you get
#3BE409. If the color is desaturated by 10%, the color
#43CC19 is obtained.