My oil pan leaks (of course) and I noticed it has offwhite/grey silicone all around it, I hear that means it's a reman and mazda didn't use silicone at build time?

 

The (1993) engine core I just turned in had the white/gray sealant around it. It was without a doubt the original engine. The reman I got in return has pink gasket sealant.

 

if it is showing that much someone may have tried to fix the oil leak with some silicone sealer instead of taking the whole pan off and putting on a new gasket.

 

No, the remans just use THAT much sealant, about 2x what is required for a given job. Pink or clear/white can indicate a reman. The factory also used sealant, btw. Usually if there's a mm or 2 worth of extra sealant, it's original, and if there's about a pinky-finger width worth sticking out, then its a reman.