Match a brand palette

With hex codes (gradient)

1. Click Custom hex palette → under the colour-mode dropdown, or choose Gradient and the preset Custom ….
2. Paste your hex codes into Paste palette, for example #1ea84a, #4ac8d8, #a878ff. Any separator works, with or without #, three or six digits.
3. Press Apply palette. The colours become stops spread evenly across the bar (up to 16).
4. Fine-tune a stop by typing a #rrggbb into its hex field, moving its position slider, or using the colour swatch. + add stop inserts one in the largest gap, × removes one (two stay as the minimum).
5. Press Save JSON to keep it. The stops travel with the preset.

The same custom gradient is available in Posterize mode (choose Custom … there).

With a formula (cosine palette)

1. Switch the colour mode to Cosine.
2. Pick one of the seven ready-made palettes as a start.
3. Change the twelve numbers: a is the base brightness, b the swing, c how often each channel cycles over the ramp, d where it starts. The strip above shows the result.
4. Use whole numbers for c if the ramp should close its cycle (lowest and highest value get the same colour).

Editing any number switches the palette to Custom; the numbers are saved in the preset.

Details of both editors: Colour modes and relief lighting.