The hex color #645c6b is a dark color. The web-safe version is Hex
#666666. A complementary color is
#9BA394. The grayscale version is
#646464. A 20% lighter version of the original color is
#978F9E, and Hex
#312938 is the 20% darker color. If the color is saturated by 10%, you get
#645B6C. If the color is desaturated by 10%, the color
#645D6A is obtained.