I think the horrid red and black is the away, and this has shown up as a potential 3rd kit:
<a class="postlink" href="http://www.aliexpress.com/item-img/Best-quality-2013-2014-Manchester-City-Gray-3rd-away-uniforms-soccer-kit-football-training-jerseys-and/931166023.html" onclick="window.open(this.href);return false;">http://www.aliexpress.com/item-img/Best ... 66023.html</a>
which I hadn't seen before.
The reason I think this is because on the OS it lists the goalkeeper 2nd kit as black, so therefore that black and gold away kit would make no sense as then both our away kits would be black.