I used Loc-tite a LOT in the largest snack manufacturer of the US. We learned the difference in the colors, and they are quite useful to anyone who deals with machines, guns, cars, etc. Please look up the chart they provide for really detailed info.
Purple is the lightest holding power for very small screws, which are easily removed.
Blue is the next level of holding power, normally needing a handtool to remove. Bolt sizes are 1/4" to possibly 3/4"
Red is a much stronger holding power, and many times requires a heating to 350 degrees + a tool to remove.
Green is a unique animal, made to 'creep' into an assembled unit and lock it down tightly. Strong hold, from my experience.
Their primer is a good cleaner and bonder, which can gain about 25% more strength in the right conditions. I rarely needed it though.
Their detailed charts will tell you which one is recommended for temps, holding needs, dissembly needs, etc. QUITE useful from what I have seen.
An important detail about their products: Less is more, in many cases. The charts will tell you full coverage, 1/4 coverage, etc based on the bolt size and the usage requirements for that bolt. DON'T assume that if some is good, more is better. Sometimes yes, mostly no.
It works in the absense of air, which means it will begin to cure within 1 hour of being installed. As long as its exposed to air, it remains liquid.
If you place it on a bolt and DON'T install it right away, it might be good for several hours, up to 1/2 a day. Once cured, it remains at full strength
unless the seal is broken (bolt backed out or removed).
In my opinion, it's great stuff with no real negatives. If you don't like it, it's easily stripped off a part when dissembled. I've found nothing which holds as well. NASA uses it. I keep the Red and Blue in my workshop at all times.
If you don't like the mess of the liquid bottles, they do make a chapstick style which is very handy.
And NOOO! I'm not a salesman here.
I just know its a superb tool that everyone should try. It's cheap insurance against our common issues.
If anyone says mean things about Loc-tite, I'll probably cry......