I recently purchased a lovat green kilt jacket which unfortunately didn't come with a matching waistcoat. I have an engagement coming up towards the end of October, and find myself needing to find one... but I can't find anything that matches my coat exactly (Lochcarron Robert of Duhne, I believe). Black Argylls all over the place, but very little in lovat green. I've found a place or two that will make one to order, but as that would likely take more time than I have available, I'd rather get something in a stock size and take it to the tailor if necessary. And even then, it'd be tweed - which my jacket is not. I have a couple of questions about how well a waistcoat which doesn't actually match would work.

1. Would a waistcoat in another colour fit the bill? In particular - charcoal grey, which is significantly darker than the lovat green.
2. Would a tweed waistcoat, regardless of colour, be off-putting?

Thanks!