There is nothing in VTK that allows you to easily import colormaps. So it is hoped that these examples address this and make it easier for users to import or create their own colormaps.
Hopefully this will make VTK a more colorful and happier place!
These two Python programs will allow you to generate and visualise XML or JSON colormaps on a cone (a sphere is also provided - commented out). They also have the ability to generate a C++ or Python function that you can automatically incorporate into your code.
These two examples demonstrate how to do this using the autogenerated function from either of the above programs:
These tools were inspired by this discussion: Replacement default color map and background palette. I have used the Fast colormap from this discussion.
A good initial source for color maps is: SciVisColor - this will provide you with plenty of XML examples.