I noticed a mistake in Fallout 4. I fought several Glowing Mutant Hounds but why are they not glowing green? Could it be because the green glow is internal and not visible on the outside of its body?

I've noticed this as well. My glowing mutant hounds are never actually glowing. It's probably just some kind of bug.

Probably when they made the Glowing Mutant Hound actor, they duplicated it off of the base Mutant Hound and forgot to redirect the model to point to the Glowing Mutant Hound model instead. Definitely an easy mistake to make, probably just as easy to fix.

I think the glowing mutant hound does extra radiation damage to you when it bites.

Anyway the glowing hounds are healthier and do more damage.

Sometimes they take me by surprise when it's dark so it's probably better for them with their sneak attacks that they aren't lit up.