A new friend of mine found out that I reload and that I have a .308 so he save me a large ziplock bag stuffed FULL of once fired Federal Brass.    

As I was going through it, I noticed the cases all had the same headstamp "F   C    308 Win"  but the primers came in 3 different "flavors".    About 20% had brass colored primers,  25% had silver primers and the rest all had silver primers with either a thin blue sealant or some other kind of blue mark on the primer/case.  

The other day I happened to be researching Federal Gold Metal 308 ammo and I noticed this blue mark on some of the pics (see below).    
Do these blue marks or different colored primers mean anything?

Current production Federal GMM .308 ammunition uses blue sealant and silver colored primers.  Some other current production flavors of Federal .308 ammunition might also use blue sealant as well (I'm not sure which).  Blue sealed "FC  308 WIN" are the only federal cases I will pick up at the range.  They are pretty consistent...  well over 90% of my cleaned, sized and trimmed cases weight in at 176 (± 1) grains.  I have had very good success reloading them.  They are predictable and have good case life if you don't beat them too hard.  I have cases with well over 10 (bolt action) load cycles on them but for me, 10 cycles is where I started to lose cases.  The 2 most common problem causing case retirement for me are incipient case head separation (ICHS) and loose primer pockets.  When I learned to control my sizing more precisely, I don't see ICHS any more, now (for me) it's loose primer pockets that is the killer of cases.  I've never had a cracked neck although I do use a FL sizing die with a neck bushing and no expander.  Blue sealed "FC  308 Win" is my favorite brass to reload other than the more expensive classics like Lapua, Alpha, Peterson, etc.

Does Federal use the blue sealant on any of their other .308 ammo besides FGMM?

A guy at the range gave me about 40 or so pieces of 1x fired .308, with silver primer and blue sealant.

Curious if it was most likely FGMM brass (which I have found to be pretty good brass).

From what I have seen fgmm cases are marked fc and the year. I belive the cases marked fc 308win are from there hunting and plinking stuff.

From what I have seen, that is absolutely incorrect.  I have several hundred FGMM .308 Win cases in my posession and not one has the year on it.

IIRC, Lake City brass (made by Federal) has the year in its headstamp tho...

All the fgmm I have is marked FC at 12 o clock and the year at 6 o clock. I'm  sure therer are other cases they use but all the stuff I have personally shot the last few years is marked how I described.

Can you post a pic?  All the cases I have seen look like the ones in the OP.

This.

All of mine are just that, FC 308WIN, silver primer, blue sealant.

I've had sporting loads in the same cases, can't tell the difference. I believe they come off the same line.

LC LR cases are also pretty good, but require a touch more powder to give the same velocity. I haven't worked it up yet, but it's looking like .1-.2gr for 175gr SMK with ARCOMP. They're about 15-20fps slow.

That's good brass, if you don't want it, Ill take it.  I make a near duplicate of the FGMM load using federal brass with a Speer 168gr BTHP and 43.5gr 4064.

Federal uses the primer sealant on their Tactical ammo as well.