Gingerbread houses!

So I’ll say they are easy to farm and have decent loot! They usually bring a lot of PvP as well but my question is how long does the no damage timer last? I’ve noticed when being camped or camping them from The inside the names are usually red for a second or two then go white. Idk how many times I have died now by being camped and hitting invalids when I portal through. Earlier I had three guys waiting for me on the other side and I stayed inside till the radiation killed me because I knew there was no winning on the outside. Also I noticed the door flickers red does that indicate someone is on the outside?