I would consider changing the buttons on your coat, I think they should match the fabric, black buttons would make me more conscious of what I was wearing with the coat, they would bug me basically. Green buttons would make it easy to wear any colour, IMHO. I like contrasting colours, that colour of green goes well with black, navy, brown, but you could wear red, yellow, turquoise etc, you could keep it casual and it would work for more dressy occasions. I am sure a good alteration service would change the buttons for you, finding the right match probably wouldn't be too hard and it would make it more special.