Revise colour palettes

[guygriffiths]

We should look through the available colour palettes and see if there are any that could be pruned or added. One user has requested more varieties of divergent colour scale, for instance.

The default scale should probably not be rainbow, but some kind of perceptually-linear colour map (google for "cube helix" for instance).

Note: This issue has been automatically migrated from Bitbucket
Created by jonblower on 2014-08-18 08:18:52+00:00