Changes in the robot's position are reflected less strongly in the readings of the color sensor than those of the light sensor - that is, the same angle seemed to induce less of a change in the color sensor's readings. We therefore speculated that we needed to multiply the error by a larger value in order to adequately correct the robot's position, which means that a larger value of p might result in the robot balancing better as the change in reading would then have a larger effect.