The hex color #51a9e1 is a light color. The web-safe version is Hex
#6699CC. A complementary color is
#AE561E. The grayscale version is
#9E9E9E. A 20% lighter version of the original color is
#84DCFF, and Hex
#1E76AE is the 20% darker color. If the color is saturated by 10%, you get
#49AAE8. If the color is desaturated by 10%, the color
#59A8DA is obtained.