Just what it says on the TIN, does DD have his(her?) own camo index? If he does indeed have his own index, does his color affect it?
No, DD doesn't have his own camo index, not that he'd need one anyway.
The thing is, when enemies notice DD, they just shoo him away like they do with every other animal in the game. They do not go investigate the places DD was at, nor do they stop investigating the places you were seen at after shooing DD away, so him following you doesn't affect your stealth play that much.
And yes, DD is a boy, assuming we can take Ocelot's words for it.
One thing you might want to keep in mind:
If you're trying to listen in on an enemy conversation, it might be best to dismiss DD depending on the situation. DD isn't disciplined enough to wait someplace for too long (thanks for training him, Ocelot), and if your eavesdropping targets notice DD, they'll interrupt their conversation as they shoo him away and might not resume, forcing you to reload your checkpoint or even restart the entire mission.