Free tools / CSS colour
CSS colour converter
Type a colour in any of hex, RGB or HSL and read it back in the other two, with a swatch to check it by eye.
Swatch
Valid colour
The three notations describe the same colour three ways. Hex and RGB both give the red, green and blue channels from 0 to 255, one in base sixteen and one in decimal. HSL gives a hue around the colour wheel in degrees, then saturation and lightness as percentages, which is the form that is easiest to adjust by hand.
Type in any field and the other two follow. Three-digit hex is expanded, spaces and the wrapping function are optional, and a field that does not parse turns the swatch off rather than guessing. CSS accepts all three, so pick whichever the surrounding code already uses.