The hex color #3f81d6 is a dark color. The web-safe version is Hex
#3399CC. A complementary color is
#C07E29. The grayscale version is
#878787. A 20% lighter version of the original color is
#72B4FF, and Hex
#0C4EA3 is the 20% darker color. If the color is saturated by 10%, you get
#3880DE. If the color is desaturated by 10%, the color
#4682CE is obtained.