Sony has been dropping hints about a new color on Twitter, gold! True, the Xperia Z3 came in "Copper" but it seems that Sony wants to shift the hue towards a more noble metal.
It's been a while since we had an Xperia with a "Gold" color option, here are the last few models (some of which date from the Sony Ericsson era). We doubt Sony is thinking actual gold like the 24K gold-plated Xperia P it gave away as a contest prize in late 2012.
Either way, the latest tweet points to August 3 (next Monday) as the day of the reveal.