Well, even though the checkpoints are red, it seems that if you're behind in a race, and the players and checkpoint is off in the distance in a relative location, the players' markers drown out the checkpoint:
If the checkpoint was off in the distance and you weren't familiar with the race, I'm sure you could imagine that this could be rather disorienting (look at the map):
Same idea here, but you can see the actual checkpoint in this screen:
In Protect the Prez server, the player's markers are a rather translucent blue and brown, so the solid yellow mark will always be dominant.
You can see the president is rather far off, but even with a lot of other players near him you can clearly tell in precisely what direction to go:
He's not surrounded too densely with people in this shot so his marker is even brighter: