that is fair, I was asleep while it happened, so I didn't get the chance to see it all with my own eyes. All I know is it killed the fuck out of that board. I wish I would have copied the error cgminer was giving me.
I have a few sinks that are the same color as the sink that fell off perhaps I should remove and take a look at the thermal tape.
Aside from being copper or aluminum color doesn't really matter for the loads put on them. I suppose they could have different tape on them though, perhaps dots vs a square. (Hope not.) The anodizing on aluminum sinks is just ascetics. If ya wanna get picky, flat black is best with measurably but still marginal better radiative dissipation..
Definitely check/re-tape the chipsinks and even better find something bigger to use.
Definitely make sure there is good airflow channeled over them as well.
What I mean is they were all copper, but they changed color due to the heat of the chips,
looks like it;s the oxidation process taking place at diffrent levels of heat.
I can snap some pics to show you what I mean if interested.