Here's where the color fun began.
I use a combination of the Polygon Lasso Tool and the Eliptical Marquee Tool to create selections for cobble stone areas and grassy areas on the "tiles" grid layer. I saved each selection using the Select/Save As function, so I could alter the colors, contrast, dimensions, or any other aspect of these seleactions later on.
(Advice: When you save a selection, immediately save the document. I usually save the document as a new name -- i.e., Mansion 09 becomes Mansion 10. Why? Because if you don't save it, you may scroll back up the History bar to a point before you save the selection without realizing it. Doing so eliminates the selection you made with such care. This sucks. Trust me on this one!)
I then tweaked the color of each outdoor selection using Image/Adjust/Hue Saturation and Image/Adjust/Color Balance to begin creating the sense of pavement and grass.