there are different temperature ranges of RTV silicone. you have your 'normal' black junk, then the red RTV (for high-temp applications; i.e.; valve covers, etc.), and the blue water pump RTV is just more resistant to coolant chemicals (glycols, other addatives) and is safe for thermostats (doesnt corrode sensors).
GOOP is just...well, GOOP LOL!! like plumbers goop, etc. its kinda like silicone, but not
