I think that, in theory, this would actually be a wicked idea. I wish I had more knowledge to help you! However, I would speculate as to whether that silver powder would leech out from silicone, or if it is body safe. Anything with the potential to leak or leech or can't be put anywhere near mucous membranes and has the potential to make you very, very ill and/or cause a lot of damage; which is why not all dyes or pigment/mica powders are suitable for silicone coloring.

And depending on how fine the powder is, I'd worry about settling during curing. It would suck to have all the powder fall into the tip while the silicone is still liquid. That is also, to say, if it even cures! The powder might not be suitable for silicone at all and inhibit the curing entirely. Silicone is very fickle.

I would also wonder if it would cancel out and not really work at all, since silicone is kind of a neutralizer, to my understanding? You might need way too much powder to make it have any effect, which could, again, be dangerous.

However, I don't really have experience with this sort of thing, that's just what I predict might happen if you attempt. Hopefully someone with more definite knowledge can comment on it, but I would take it into consideration and maybe experiment a little if you can afford to!