I found this on the Loctite website,,,,

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