Mark,

You probably want the purple loctite since a threadlocker is optional anyway - I think this is the #222 / small screw threadlocker; this breaks loose easily but does protect against vibration.  I know that the blue is #242 (removable) and is what I usually use but it can require pretty high force to break loose. The red is #262 (permanent) and can be pretty tough to get loose and sometimes requires heat.  They seem to make a product for everything - the RV guys have even found that the green (#290 I think) will stop a leaking gas tank rivet!  I bet Bill Jepson has some real war stories about this stuff!  The dirt bike racers keep the bikes together with this stuff since they don't usually use safety wire.