Is the red that appears on gold coins normal toning. If yes is it always red/orange or can it be other colors?
I believe it's copper spotting. It can happen when gold alloy is not well mixed, or particular copper dropplets on the coin. There can be a possibility of "greenish" toning, but I don't think there can be much toning unless your gold is not really "gold" as in, <80~90% pureness.
You mean like this ? As gx said, they call it copper spotting. But that particular coin I posted just above is .986 gold - and it still has the toning. Gold can and will tone under the right conditions. And most of the time it is of a reddish, orange or pinkish color. Quite often you will find older gold coins that are up for auction as having rose colored toning - that's what I call pinkish - rose just sounds so much better Most folks will tell you that gold doesn't tone. It doesn't always, but it does sometimes. Anyone who has collected gold coins for any period of time can tell you that. There's just too many of them out there to think otherwise. Most of the time it is due to the impurities or alloy in the coin. But as you can see from the coin I posted above that is almost pure gold - it can tone.
