You mean this map?
Reminds me on this map from Djekspek:
The mountains are a bewell and emboss thing ... you should ask Djekspek for the technique or look through some tutorials here.
But the thing is, to let it look colorful like that, you have to play around with lots of layers with different colors. Put a mask on each colorfilled layer and fill it with a rough pattern, that will make the color look more suitable. And do it with many colors, even with darker and brighter tones.