I would like to see a colour picker UI node as I think it would be a really helpful addition to the other UI nodes especially for compositions intended to export into apps. It could output either RGB or HSL values, either in a list or as individual value outputs.
This composition uses a list of color palettes in JSON format and displays a random palette every few seconds. Colors are from https://github.com/Jam3/nice-color-palettes (in this case the 1000.json file is embedded in the composition).