Thanks for the comments (and the reps)!

@Freodin: Yes, well, the labeling is indeed pretty random - last-ditch addition as the map looked pretty naked without it. Will try and work something out.

@Revock: Wow, cool! But that was not what I was looking for. Actually my intention was perhaps too primitive to be considered - I just want the colors, especially the coloring of larger areas, to be more intense, more covering and at the same time blending better into each other.
Hmmm, maybe Sinisteria was not the best example. This might illustrate things better - it looks not unlike mine, but the deeper colors, especially considering the seas, give it a completely different expression, just because there is now much more emphasis put onto the landscape. (I hope I've expressed it right, English is not my native language.)

Now while there are tutorials available on how to achieve things when you start a new picture from the ground up, I was wondering if the existing map could somehow be manipulated. That's actually all.