That looks perfectly fine. The different colors simply indicate different connected components of the graph (i.e different areas such that there is no valid path between nodes of node color to nodes of another color).
You may want to tweak your ‘Max Climb’ setting as well as the ‘Max Slope’ setting, but that depends on the game.
Thanks for fast reply. What threw me was that every other time I used it the walkable areas were coloured green, but if I understand it correctly now, they can be any colour, different for each connected patch of walkable nodes…?