Why does the view of the ground, from a plane, just look like a bunch of different colored squares?

I know it's a strange question, but I've always wondered it. Every time I fly and look out the window it just looks like a bunch of different colored squares (unless I'm flying over water or the Grand Canyon.) Of course on the ground it is not like that at all. I wouldn't think there would be such strong separation, or visible "borders." Of course there are different colors, but I've always expected it to be more smooth and blended. Does anybody know why this is?