Just as a follow-up:

Here's a video tutorial I made a few months back for XCSoar. I cover
the whole "display terrain" thing at about the 4-minute mark.

http://www.youtube.com/watch?v=swBB_ggqYFA

(I got sucked into some crazy work projects but hope to finally
produce the follow-up videos in the next few weeks)

Take care,

--Noel
P.S. The newer versions of XCSoar also have multiple color-coding
systems you can choose between in the main setup area. So you can
customize the look of the terrain to a certain extent, too.