If the sound engineer tunes for the coloured sound, and the sound that he is hearing is coloured the same regardless of whether he is wearing ear plugs, does it not then follow that the sound that you are hearing is coloured the same regardless of whether you are wearing ear plugs?
* Sound engineer is wearing ear protection -> sound is tuned according to that bias (unless they are completely auditory neutral) -> you get the best sound by also wearing hearing protection
* Sound engineer is not wearing ear protection -> sound engineer probably has hearing damage due to prolonged exposure (and has a similar effect as hearing protection) -> sound is tuned according to that bias -> you do NOT have hearing damage, so you get the best sound by wearing hearing protection
The effect on the sound is the same in both cases and the correction is the same in both -- wear hearing protection. It only becomes the same sound regardless of what _you_ do in the long term, if you also get hearing loss due to prolonged exposure.
