I think it looks fine. I really like that jacket conversion!

But the beret looks good and goes well with the outfit. Although, I am sure someone will chime in to discuss the significance of color and "entitlement". I hope I am wrong about that. To be honest, I don't wear hats with my kilt much because I don't care for the traditional headwear. I like this because it is similar and I might give this a shot--probably I'd go a bit more casual with it (just for me).