Silver washed with agrax earthshdae should do the trick. Alternatively Relictor gold suitably washed looks like it would produce a similar effect as its a very pale gold.
I certainly wouldn't say you need to mix anything for this, generally any metal tone can be achieved through a silver or gold with the right wash (and plus its much easier to replicate).
Me: To be honest im amazed there isn't a chaos god of not revising or at least chaos god of procrastination
MidnightSun: There will be, when enough people do it. Y'know when the Eldar were all engaging in their hedonism and Slaanesh ripped open the Eye of Terror with his creation? Slaanesh will have NOTHING on the God of Procrastination, and his vile minions will carve the galaxy asunder in a thousand year reign of blood.... Tomorrow