I have a bunch of old 4" GeoHex hills that I use on a playing mat that I textured a long time ago (12 years? maybe 15?). They are on the left above. I have been repainting them to match the mat and the troop bases (right). There is a slight colour shift in this image so the new paint looks a bit dustier than it is in person.
Since I'm using the same paint colours, the match to the bases is almost perfect. There are a couple of dozen hills to do so I am slowly chipping away at them.