Installation

clone the git repository somewhere on your system: git clone ...
install a python version that is compatible with blender (e.g. python 3.5.1 for blender 2.77a) and install the colorspacious module with pip install colorspacious. This is straightforward with anaconda python: first make a virtual environment with conda create -n blender python=3.5. Then do source activate blender to activate the environment and install colorspacious with pip install colorspacious

The `colormap.blend` project file

open the project colormaps.blend with blender.
click on the different layers (little boxes at the bottom right of the 3d view windows) and check out the objects that are within each by doing a right click on the objects. The layers are organized like this:

layer 1: contains a precomputed Gamut surface and can be used to position a surface or path in the Gamut to compute the colormap
layer 2: this is the render layer. Computed and colored meshes can be put here for advanced visualizations
layer 3: this is the dump layer for lots of different spline surfaces and paths that are ready to be taken to layer 1 for colormap computation
layer 4: this is the dump layer for modified, and colored non-spline surfaces or paths.

in the python script Add_Gamut (can be selected on in the footline of the text window on the right), change the path to point to your colorspacious module. E.g.: sys.path.append('home/myname/anaconda2/envs/blender/lib/python3.5/site-packages'')
run the script with alt + p when the text window is active or click the run script button in the footline of the text editor window. A new Gamut surface is generated. You can modify the resolution of the Gamut cube in the script.

in the python script path_to_colormap (can be selected on in the footline of the text window on the right), change the path to point to your colorspacious module. E.g.: sys.path.append('home/myname/anaconda2/envs/blender/lib/python3.5/site-packages'')
you can now add and edit the control points of bezier curves in the 3d window. If you are done positioning your curve, make sure that it is selected and run the python script by pushing on run script or pressing alt + p when the script window is active. The colormap on the bottom left should now update.

in the python script nurbs_to_colormap, change the path to point to your colorspacious module. E.g.: sys.path.append('home/myname/anaconda2/envs/blender/lib/python3.5/site-packages'')
you can now add and edit the control points of nurbs surfaces in the 3d window. The u and v resolution parameters control the axial and angular sampling of the cylinder and can be reduced while editing. The spline order controls the smoothness of the surface.
If you are done positioning the surface, make sure that it is selected and run the python script by pushing on run script or pressing alt + p when the script window is active. Be careful, the script generates a duplicate of the nurbs surface that you can delete after the colormap has been generated. The colormap on the bottom left should now update. There is a parameter in the script to transpose the colormaps and a commented line to save it as a npy file.