It includes four colormaps: viridis, plasma, inferno and magma. Examples of these colormaps can be seen here. You can use them in gnuplot by adding the following line to your script:
load 'plasma.plt'
Replace plasma.plt with desired colormap.
Original colormaps are designed by Nathaniel J. Smith, Stefan van der Walt and Eric Firing, licensed under CC0. colormap.py is a fragment of this file.