DH is red-green colorblind. When driving he thinks of lights as top-middle-bottom rather than red, yellow, and green. And he takes cues from how other traffic is moving. He says sometimes a stop sign can be hard to see if there is a lot of foliage around it. On the bike he is way faster than me on flats and downhills, but mostly when we've ridden together it is in light traffic conditions. I don't think it really affects his ability to negotiate through traffic; he just has pay attention to what's going on around him . . . . like the rest of us.