You can get to Colour Group via Developer » Color Group.
Groups by number The Groups by number tab creates colour groups on the basis of the first number of the component reference meaning if the refernce is "R123" it would be 1. Usually components belonging together are grouped by their reference number during circuit diagram creation. The colour coding thus allows you to recognize with one glance how the individual functions have been distributed throughout the curcuit board, for example, having all components belonging to the power supply coloured in a deep yellow.
Groups by char Grouping by char is very similar to grouping by number with the sole difference being that group by char depends on the first char of the component reference rather than the first number whereby the first char in turn usually is dependent on the type of components (R for resistance, C for capacitor, L for coil, etc.).
In both cases the colour scheme can of course be customised to fit your preferences.