I checked several references. No indications whether the compound is silver based or silicone based. However, like AsAn Atheist, I do not think it is silicone based. That would be unusual.
The recommendation is to reapply thermal compound once a year.
I haven't used AS5 for quite a few years. No ancient recollections.
Hmm... Your right, I can't find any references for it. I made the assumption it was silver based but it appears it isn't.
Nm the indigo.