With PamPam you can customize the color theme of your map, there are a few options to pick from. To change the color theme:
Click into "Edit" mode, in the toggle in the top right of the panel
In the bottom toolbar, click on the color palette
Click on it until you find the desired color theme
Limitations
At the moment there are no other customization options for maps on PamPam:
You can't bring in your own color themes
You can't add terrain