Coldtone (as the name suggests) gives a slightly cooler feel to your world.
Everything is slightly blue, grey and violet tinged, though pure warm colors are included in many of the pieces.

The original inspiration was working on a world that was extremely mountainous with a lot of snow and ice, but the dirt and wood seemed so warm colored that it really stood out from the in-the-mountain habitat I was building.

Thus came the cold!

Fret not, dear desert living types. Sand is still sand and cacti are still cacti!

See the thread on minecraftforum.net for more info and quicker updates!