I fell on the following incoherence at using colormaps. The way colors are mapped on nodes can be tuned using an interactor from the Histogram view. You see the colormap on the side and adjust the curve according to the metric distribution.
The rainbow colormap is the default colormap used when invoking the Color Mapping plugin. The same rainbow colormap shows up in the histogram view when activating the color map interactor.
Now, the Color Mapping plugin lets you select from a large choice of colormaps.
However, when going to the Histogram view, using the color map interactro, you still get the rainbow colormap on the side.
You have to manually change it (by double clicking it). Would be nice if the colormap used on the graph would pop up when activating the color map interactor.
note that this may be tricky since you may use different colormaps on a graph and subgraphs. Not sure how the association graph (and subgraphs) <-> colormap(s) need to be tracked.
The colormaps management has been dramatically refine in Tulip 4.10.
The latest chosen colormap is now registered and proposed as soon as there is a need for a colormap. This latest chosen colormap is also retrieved when beginning a new session of work with Tulip.
I hope this will satisfy most of your needs.