Pay dirt?

Here's some Oklahoma dirt for you. Red clay. For rivers and lakes, just imagine the water image magnified a million times. Not all water here is red, of course, but that shown here gives you a good idea of what 80% of the homes look like, and this is cool. Because...it results in consistency. Block after block of houses share similarities of color and materials, qualtities related to the earth about them, and their unique qualities are found in their forms and the vegetation that surrounds them. I like this. It reminds me of what I see everywhere in France, where stone is a commonly used building material and one can see that it comes directly out of the surrounding earth. In the Northwest, our use of wood, requiring protection through paint, results in a real collage of colors that can sometimes be chaotic. I'm becoming an Okie snob! Now as far as the pay dirt part of it goes, I have no idea what the best color for oil-rich soil is? Do you? And by the way, I'm learning to say "ahlll" for "oil."