This option is intended to make it easy to quickly give routes and tracks different colours, to more easily identify them on the map.
Select select the routes and tracks you wish to change and choose the
Assign colours to routes and tracks from the Edit menu of the
Features tab. After confirmation each colour defined on the system is
assigned to each route and then each track in sequence. If there are more
tracks and routes selected than there are colours, the colours are repeated
from the beginning again.