I have been both orange and blue and, frankly, every time I couldn't wait to get back to white. This was mostly because of the hassle it creates in safe waters when I'm there to do things other than battle. I believe that current rules are that bounty hunters can not attack privateers from their own country. I would suggest extending this to only allow bounty hunters from countries with which you have negative relations to be able to attack privateers in safe waters.
The rationale is there as well: if a Spanish privateer is only attacking French players, why would the English care? In fact, the English may appreciate that the Spanish privateer is essentially doing their dirty work for them. I might be more inclined to go orange knowing that the "pool" of players who can attack me is much smaller in safe waters. It could also create some interesting inter-nation dynamics and force me to pay attention who the active bounty hunters are.
Just a though...