With enough practice, a person can even tell the size of those rocks, and that can make a big difference. Fritts is such a masterful crankbait fisherman that he can gain similar information through his diving baits. As the big diving bills of the baits drag the bottom, his experienced hands can differentiate between a hard bottom and a soft one, and they can indicate the presence of cover such as stumps, rocks and weeds. But few understand the other seasonal ramifications as they relate to bottom composition. There are exceptions, but if you can keep your boat over a good, solid bottom, your odds of catching fish will be better.
Color can make a difference as well.
The dark-colored terrain retains heat better than a lighter floor. The muck on the bottom will absorb that energy and then transmit it back more directly into the water. So this is where you find the early pre-spawn bass. In spring, the spawning urge becomes a major factor in developing patterns, so then you're looking for places where bass can find a good, hard substrate. They will seek out places where the harder bottom prevents their eggs from being covered by silt.