The hex color #3991cc is a dark color. The web-safe version is Hex
#3399CC. A complementary color is
#C66E33. The grayscale version is
#878787. A 20% lighter version of the original color is
#6CC4FF, and Hex
#065E99 is the 20% darker color. If the color is saturated by 10%, you get
#3192D3. If the color is desaturated by 10%, the color
#4190C5 is obtained.