From Marathon Documentation
Favourites
1. Open the column alternative box (grey box outmost to right in a list’s header row) and select colours to use in your list. Five different colours can be used in one list. Click on the colour dot to change colour."
2. Click in the favourite column at outmost left in all tables and select your favourites. Click several times to change colour.
3. Click on the header of the favourite column to change different colour displays"
4. Continue clicking to see only one favourite colour.