If you are replacing a Bermuda grass lawn with buffalo grass, you will have to kill any Bermuda that survived the pre-planting attempts to kill it. There will be sprouts for several months, maybe even years, depending on how long the Bermuda Grass had to become established. You can either dig out the sprouts, removing as much of the roots as possible, or carefully spray them with a grass-killing herbicide. I'm doing both, depending on how close the Bermuda grass sprout is to the buffalo grass.
They are both grasses, and both spread by runners across the soil. So how do you tell them apart? Look at the way the leaves grow.
This is Bermuda grass. The leaves come out almost opposite to each other. As the runner gets longer, a new pair of leaves will push out of the growing tip.
This is buffalo grass. Only the leaves at the tip are paired. The leaves on the runners are not paired. The growing tip will leave one of the blades behind on the stem as the runner gets longer.
More Bermuda grass. It typically has the blades parallel to the ground, flat side up to catch as much sun as possible. The leaves are mostly in pairs.
More buffalo grass. It tends to send the sprouts upward instead of flat to the ground.