bzrtools - graph-ancestry: question about colors

[Alexander Belchenko]

graph-ancestry if amazing plugin. I like it so much.

Today I trying to create graph for my project with --merge-base options.
After creating graph I've got picture that have following colors:
blue, orange, red, yellow and green.

There is legend for colors in help:

Legend:
white    normal revision
yellow   THIS  history
red      OTHER history
orange   COMMON history
blue     COMMON non-history ancestor
dotted   Missing from branch storage

In legend I found no mention about green color. Is this intended 
behaviour? Or just not described in help?

Produced graph is here: http://bzr.onembedding.com/graph/bialix.png
Graph (as relation between branches and revisions) is correct.

Alexander