The red looks good. I think the reason you may uncomfortable with the white is because of that "light fabric jumps out at you" phenomenon. By using color in the edge squares, you are actually popping the sampler squares forward.
I prefer the red (but that is because I am old! LOL feeling a little danger, I guess). Having watched a ton of decorating shows, the green is something that makes one think of the sea/ocean/water ... and, is supposed to have a quieting effect ... and, I thought it was a good match.
Red white and blue ... traditional ... and while yellow, white, blue is a clean look, suddenly throwing it in on those edges is as jarring as the white is ...