You have already covered how to add vision to your BeagleBone Black project. A great addition to your mobile robot is the ability to follow a colored object attached to a target.
Remember how you used OpenCV to find a colored object, and could then find out where in your field of view (left or right, or up or down) it existed? You can use this to decide whether to move your mobile platform right or left, or forward or backward. Try this, and then move the target to see if your mobile robot can follow it.