I think hawk eye is some sort of haki and the darker it is the stronger it is. It would probably take centuries of training to get the darkest colour eye
green eye = lowest level caribou and zounisha has it (power unknown) despite living for centuries it came automatically to zounisha but for caribou he might know the technique as he spies around many places.
orange eye = half way of getting it to dark and also known as hawk eye. Mihawk didn't live for centuries but probably knows the technique and went through difficult training session. Also hakuba probably inherited but doesn't know how to control it just how luffy didnt know how to control his haki pre timeskip.
red eye = the darkest eye and imu has it. Could also mean imu lived for centuries.
Will Zoro unlock the red eye at the end of one piece but only one eye? Able to overtake mihawk at the end.
Is hakuba related to Imu?
green eye = lowest level caribou and zounisha has it (power unknown) despite living for centuries it came automatically to zounisha but for caribou he might know the technique as he spies around many places.
orange eye = half way of getting it to dark and also known as hawk eye. Mihawk didn't live for centuries but probably knows the technique and went through difficult training session. Also hakuba probably inherited but doesn't know how to control it just how luffy didnt know how to control his haki pre timeskip.
red eye = the darkest eye and imu has it. Could also mean imu lived for centuries.
Will Zoro unlock the red eye at the end of one piece but only one eye? Able to overtake mihawk at the end.
Is hakuba related to Imu?