Different speeds in horses of the identical color/pattern

In the weekly update on 19 April horse breeds were described as having different attributes such as speed and jump height. I assumed the breeds could be identified by color and that horses of the identical color would have identical speeds. But in running a speed test using Sethbling's command block stopwatch, I found horses of the identical color have different speeds. In my test, I compared to solid brown horses. Results of multiple tests of the same horse varied by only 1 point. But results from two different horses of the same color varied by 6 points.