The fenders come to the factory painted black which is why I think there is a lack of options out of the box. This however being Morgan, anything is possible depending on the depth of your pocketbook.
The company who makes the wire wheels have a couple different options for rims, so chances are this can easily be swapped out. Either by you, or I am sure by the factory.
http://shop.mwsint.com/product_details.asp?id=63Morgans have "standard colors" for body paint and leather, but you can also get it painted in any color of your choosing off a color wheel or from preexisting paint.
In some ways, I do feel you may be better off ordering something standard from the factory and editing such cosmetic changes on your own or at a local paint shop.