What this tool does
The color picker shows one color three ways at once: HEX for the web, RGB for screens, and HSL for design work. Click any value to copy it. Below the values you get ten related colors: five shades (the same hue, progressively darker) and five tints (the same hue, progressively lighter).
How shades and tints are made
The tool converts your color to HSL, then steps the lightness down by 10 points for each shade and up by 10 points for each tint, keeping hue and saturation (mostly) fixed. Tints also ease saturation down slightly so very light steps do not look washed out.
Worked example
Pick #3B82F6 (a medium blue). Its values are rgb(59, 130, 246) and hsl(217, 91%, 60%). One shade down is #1D66E5; one tint up is #6CA3F8.
When to use which format
Use HEX in CSS and HTML, RGB when an API or tool asks for channel values, and HSL when you want to adjust a color by feel (nudge the hue to shift the color family, or the lightness for dark mode variants).
Limitations
The picker works in the sRGB color space, which covers standard web and screen use. Wide-gamut formats like Display P3 are not represented.