What color is the snowshoe rabbit in The Call of the Wild?

The snowshoe rabbit is white or light gray, because it is hard to see in the snow. 

Dub is the one who sees the rabbit first.  He gets it started running, but is unable to catch it.  As a result, all of the dogs go after it.  The rabbit is hard to see, however, making chasing it a difficult task.  For one thing, the rabbit is light enough to run on the surface of the snow, but the dogs crash through it. 

Buck led the pack, sixty strong, around bend after bend, but he could not gain. He lay down low to the race, whining eagerly, his splendid body flashing forward, leap by leap, in the wan white moonlight. And leap by leap, like some pale frost wraith, the snowshoe rabbit flashed on ahead. (Ch. 3)

Buck enjoys the hunt.  He is getting wilder and wilder.  As he hunts the rabbit, he is enjoying himself.  Then he notices that Spitz is after it too, and he realizes that the two are about to do battle.  This time it will be a fight to the death. 

Buck did not know of this, and as he rounded the bend, the frost wraith of a rabbit still flitting before him, he saw another and larger frost wraith leap from the overhanging bank into the immediate path of the rabbit. It was Spitz. (Ch. 3) 

It is the nature of the wild for things to change in an instant.  Buck went from being one of sixty dogs chasing a rabbit to fighting for supremacy with Spitz.  The conflict between Buck and Spitz had been growing, and since everyone’s blood-lust was raised by the rabbit, it erupted into a challenge. 

When Buck killed Spitz, he became the leader of the pack.  The men are a little surprised, but they come to accept that Buck wants to be leader and is a natural leader.  They agree to let him become lead dog, since he insists and will not allow any other dog to be placed there.