I'm in the process of having two brass cantled sporrans made for me (which I hope will be done next week). Both have a cantle exactly like Peter's above. One will have seal fur and the other a very light color buff leather bag. The fur one I imagine I will wear for evening wear, while the leather one I will use for day wear. However, I see no reason why I couldn't wear either of them any time. I'll be sure to post pics when they come in.

I currently own a brass cantled sporran with a different design cantle and dark brown leather bag. I tend to use it for day wear, not evening wear, but I'll wear it for varying degrees of formality in my day dress, as seen below.








I'm not really one to say "yellow metal for day, white metal for evening." I know this is the general rule of thumb for many, but I see no real reason why someone cannot wear brass or gold for evening wear -- people already often wear silver, nickel, or chrome for day dress these days anyway. I'll often wear both white and yellow metals at the same time. To be honest I don't really give the color of the metal a thought in this regard.