Many of the ball techs I have come across where the gold is in reasonable condition actually had a laquer on them which over the years ends up a nasty orange colour. It's most noticeable in the indents at the end of handles under the ball and in the bottoms of the knurling. Some of the fat techs appear to have had a similar treatment which goes orange - although because of the design of the fat techs, it's usually long gone as most of the surfaces get an even wear which results in it being lost.
I totally agree with Carl though, gold is the most amazing metal in terms of never ever tarnishing - if it definitely is gold still and hasn't worn through, it shouldn't need much more than a gentle wash with something fairly simple like some dishwashing liquid and a soft toothbrush to remove soap scum from groves etc. The worst areas on the fat tech tend to be where the main handle has the top threaded section joined to it and the base plate where you tend to have lots of nooks and crannies for muck to lodge. Whatever you do don't use anything abrasive on it like Brasso or any similar products. The original plating thickness that Gillette used was INCREDIBLY thin and you will end up hitting the nickel below or at worst the base metal of brass.
Have you got a quick photo of the razor you're trying to clean ?
I've worked on replating lots of the fat techs and they are lovely razors and really well made. I actually restored a tech in gold today (Uncle Berties) and it has to be my favourite razor to work on.
Cheers,
Jay