I think green or yellow is a sign of infection so I'd definitely be heading to the GP.

I find taking her in a shower as hot as she can deal with is way more effective than a humidifier. I was also told on the weekend by a GP at a kids' party I went to that humidifiers aren't as good for bubs because they make the air colder, and that what you need is a vaporiser. Don't know if there's any accuracy to that but just putting it out there.

Your poor baby girl. Mine has a snotty nose but touch wood so far its clear. I hope she's feeling much better very soon.