The color picker uses the OkLCh color space. The OkLCh color space is designed for humans to interact with color. Its special property is color changes matched to human perception. It's divided into lightness, chroma (saturation), and hue. The special property allows the change in one value to not affect the others according to (subjective) human perception.
This allows the picker to be used by feel, rather than calculating exact values. The space is bigger than RGB, so some combinations of values are mapped to a nearby RGB color, those are marked with a dark red bar in the picker.
Recenter the page
Open this information page
Change palette settings
Clean the canvas, emptying the palette
Reset the palette to the default showcase
Save the palette to a (special) PNG file
Load a palette from a (special) PNG file
Remove a row/column
Add a row/column