The fabric in the pictures does not look like tweed. It looks like a worsted wool in a charcoal color.

Personally, I don't think I like it in the Prince Charlie. But there is no objective reason why you can't have a Prince Charlie made from any color you like. I've seen them in bottle green and navy blue, white, red, etc. But the "classic" is, of course, black.

However, I think the right person, with the right outfit, could make it work. I can see this being worn with a predominantly grey tartan, like the Highland Granite from Lochcarron, or any of House of Edgar's Hebridean line.