The hex color #21030a is a dark color. The web-safe version is Hex
#330000. A complementary color is
#DEFCF5. The grayscale version is
#0F0F0F. A 20% lighter version of the original color is
#54363D, and Hex
#000000 is the 20% darker color. If the color is saturated by 10%, you get
#230209. If the color is desaturated by 10%, the color
#1F040B is obtained.