A colour palette is a [[data tiddler|DataTiddlers]] that supplies a [[CSS]] colour value, such as ''yellow'' or ''#fe0'', for each of several colour names, like this:
Several palettes form part of the core. The system tiddler [[$:/palette]] always contains the title of the currently selected palette tiddler. You can change a palette using the <<.icon $:/core/images/palette>> ''palette'' button, found on the "Tools" tab in the sidebar.