Does single point autofocus react to different colors?

I am shooting with a Canon EOS 50D, Canon 70-200 EF IS USM f/2.8. I shoot mostly rugby. I am having a problem with consistent tack-sharp focusing on the single player at the center of the action. It's sometimes hit and miss and I'm not sure what is happening. I use the single center focus point, dead center of the jersey of the player at peak action. Generally that player is running toward me. I've got the lens racked out to 200mm most of the time and my minimum shutter speed is 1/1000 at all times. I try to keep the lens wide open for great bokeh. That's why I bought a $1,700 lens.
One theory I wish to confirm or eliminate is the question of whether or not Canon's autofocus reacts differently to bright red/orange than it would to blue/green. In certain shots where a player's jersey is white, or blue and white, or even green, I seem to have a lot more luck with the autofocus. If the player is wearing a bright red/orange jersey, the center of the depth of field seems to be about six feet behind the player even though I've got the red dot of the single point focus right in the middle of his chest when the motor drive shutter makes the exposures. If I get off a burst of six frames, maybe one of them will be tack sharp, but then again, maybe not. I'm getting really tired of coming home from a game thinking I've got some tack sharp images (according to the 3" screen on the back of the 50D) only to open them in Photoshop and see that I just barely missed! Frustrating to say the least.