How can you give gold a patina finish?

I am a little confused with your question. We may need a little more information for a good answer.

For something to show patina, means ' we want it to look old', as in bronze will turn black and green. Copper turns black, silver turns black. I have not seen gold turn another color. I have seen gold dull or look dirty. Gold jewelry can look dull by being dulled and dirty. You shine gold and it gleems.

I am trying to understand why you would want a patina on gold. Gold can have different colors, you can tell older gold by the mixture of metals in the gold.

One thing you absolutely cannot do with gold that is easier with other metals, is try to date gold or make it look like it is from another era. If this is what you are trying to do, you would have to be an expert. There are so many tests today that are run on gold, it would not work.