Twice in the last few days we've noticed that our 6-month old has had a greenish tint to her tongue coating, that would normally be a faint white. After the first occasion we surmised it was probably something she'd been licking, but it appeared again today and we're sure that she wasn't licking any green books or toys or anything like that.
Any ideas what it might be? I found references to oral thrush and "hairy tongue" online, but they seem to be more consistent things, whereas this is something that only seems to last for a couple of hours.
She is teething right now, if you think that's relevant.