Four colour are used to draw transition arcs. The arcs in one pre-image fan are drawn in the same colour (except for the uniform states, see below). If the attractor period is 5 or less, successive fans are given a different colour so that a given transient tree may have a mix of colours. For attractor periods of 6 or more, all fans in the same tree are given the same colour, and the colour is changed for the next non-equivalent tree. Note that equivalent trees will be coloured identically.
Conventions for node colors are described in #20.2.