Newbie - Applying base map colours to faces

[AnthK1973]

Hi all,
So I have been trying the GIS add on and have an issue I cannot seem to get past.
This is the only thing I have done on Blender and so some of my issue may be due to being unfamiliar with the tools.
So anyway I have a basemap from the G command then select the area with B then E:

I then add the SRTM modifiers at 30m. As the "resolution" of the peaks is quite low I up the strength then go to edit mode and subdivide a couple of times:

What I would like to do is get this object into a form for 3D printing. That is fairly easy in exporting the object as STL etc but I want to have the object split by colour from the basemap UV. Knowing there will be an excessive number in the palette I need to reduce the number down to say 8.

My thoughts are that after triangulating the object - I essentially need the faces to have the same colour as the UV.
I then need to reduce the number of colours and select the faces by colour and create duplicate objects.

If anyone has any ideas and guides as to how to achieve this it would be greatly appreciated

Thanks,

Anthony