@Soviet most use something like World Machine BUT that said the number 8 wire fix Sorry Kiwi expression) is to load the grey scale Heightmap into photoshop or Gimp and colour pic shade ranges that you want for each colour for example the blacker ranges you copy paste into the say blue channel greys-ish (grass area’s) copy paste into the green channel and the whites into the red channel. this Aussie might help more than me lol
Hope it’s of use, happy to help if I can also. I have World Machine and world Creator