Omega Seamster Diver, screwdriver size???

Well not exactly. 222 Purple, also known as small screw/low strength threadlocker, is actually the easiest to remove of the threadlocking compounds. Blue is considered medium strength...red is high strength...green is for wicking applications.

Years ago when I organized training sessions from Loctite for the industrial mechanics at the factory where I was working an engineer, the Loctite people told us that blue was considered permanent for all socket head cap screws (most common fastener used around the pant) with sizes 1/4-20 of under. However it is commonly used for smaller threads in the watch world. If the screw thread is very small or has had too much threadlocker applied, blue can require heat to remove it.

Note that in different areas of the world, sometimes different numbers are used. Also that Loctite for other applications may not follow the same colour code = strength patterns, so things like retaining compounds are different than threadlockers.

Cheers, Al