One color, every format: type a HEX code or use the picker, and get RGB, HSL, HSV and CSS-ready values, with a strip of shades and tints.
HEX is the compact web notation; RGB describes the red, green and blue channels; HSL (hue, saturation, lightness) is the format humans adjust most naturally — keep the hue, soften the saturation, lift the lightness for a calmer version of the same color. HSV is used by most design-tool color pickers.
What is the difference between HSL and HSV? Both start from hue. HSL lightness tops out at white; HSV value tops out at the pure color. Design tools often show HSV; CSS uses HSL.
How do I get a darker version that still matches? Keep hue and saturation, drop lightness by 10–15 points — the darkest shade in the strip below does exactly that.