Hi GR, I'd personally be inclined to match the hat to the outfit if you're going with navy for the other accessories. I agree with Dot though - I think that navy may be a bit harsh (especially for a spring/summer wedding) with a pale blue suit, and a lighter colour may look nicer. In which case, you may like to match the hat to the new colour. I don't feel that I've helped much here, but I hope I have! Hope it all goes well, and that the sun shines on the day!