Plastic Wall board or sheets

This.
They sell moldings for inside/outside/end cap/butt joints. Liquid Nails construction adhesive and you’re ready to go. It has a textured face thats glossy and easy to wipe down or spray off.

You can still get it in a variety of colors I believe too.

http://media.mydoitbest.com/imagerequest.aspx?sku=100390&size=2&warehouse=C&newsize=200