http://www.loctiteproducts.com/products/subcategory.asp?CatID=10&SubID=48
Green
Prevents vibration loosening of pre-assembled fasteners
For use on electrical connectors, instrumentation, screws, and set screws
Ideal for fasteners #2 - 1/2"

Red
OEM specified as 271
High temperature, high strength for heavy duty applications
Designed for larger fasteners 3/8" to 1" (9.5mm to 25mm)
Locks studs, bushings and large fasteners against vibration loosening
Strengthens slip and light press fits
Removable with heat and hand tools

Blue
Locks threaded fasteners against vibration loosening
Ideal for nut and bolt applications 1/4" to 3/4" (6mm to 20mm)
Prevents threads from rusting and leaking
Removable with hand tools for easy disassembly
Temperature range: -65 degrees to 300 degrees Fahrenheit (-54 degrees to 149 degrees Celsius)