I think the versatility of black grenadine or knit depends on your wardrobe. Obviously it goes well with navy and other darker blues and can work well with greens and grays. Probably less so with browns, unless you want to look like a National Socialist. Now, when you say formal occasions... do you mean actual black tie affairs or do you mean it in a more colloquial way to mean business and cocktail stuff? If the former, no, it's not appropriate. If the latter, then I wouldn't worry too much about wearing it. As for shoes, for me it usually means black.
Thanks for the response. I meant formal as in business/wedding format.
Was thinking of wearing navy or dark gray suit, white shirt, black grenadine fina, +/- square, and brown calf chelseas. I know black shoes are the obvious choice, but I recently sold my only pair (which USPS lost, but that's another issue).