How to make fake gold look less yellow?

It's my prom on Thursday and I have everything i need for it, all the jewellery I bought is gold (not real gold, just gold coloured) as my bag has a big gold buckle on it, the only problem is the jewellery I bought is a more antique looking brassy gold colour and the buckle is a very bright yellowy gold. I was wondering if there was anything I could do (for example something I could rub on it) to make it look more tarnished and antiquey rather than yellowy?