EXP 2: Landscape Integration.

This is the integration of my first landscape. What i would like to achieve here is to create a cave city which is basically underground. The reason for that is because my idea for the model that i chosen to developed is Hidden+Symmetrical. So for the landscape i would like to have a piece of land that is submarine or underground. 

But currently, the color in the image is bit fault. as i use the voxel tool to create the cave, but when i use the material under the voxel painter to paint the cave, the only thing i got is the texture but no the color of the texture.