As in 45 years of doing one thing, and he now decides to ask the internet (the most unreliable source of information).
Except that we have a member that was a Loctite Rep for 15 years so BS is a great place to ask that question and get reliable information.
Guys, I was a Loctite Factory Rep for 15 years and got that question all of the time-especially rolling up on this time of year.
A purple or blue threadlocker should be fine. Don't ever use a red permenant threadlocker on something like a scope mount.
Purple threadlockers are considered low strength and have a lower breakloose and prevailing loosening torque for removal than the medium strength threadlockers have. Red is off the charts for mere mortals.
Dirty