Photographers don't really care if you're all natural or not, just so long as you make it look good. At least that's been my experience so far!
Personally I think you don't need to tread too far from where your hair is naturally, but maybe just brighten it up a little!! You are right, lighter hair would suit you! I think maybe some very subtle but thorough highlights all throughout your hair would elevate your look and pull more focus to your face and eyes, giving you a more "from-within" glow.