I'd like to add a spare parts and repair kit to my SHTF ammocan(I'm not talking about a GI field cleaning kit, which I already carry). I have a Colt M4gery and want to carry and use only Colt parts. I noticed that Bushmaster sells a "field repair kit" which contains exta parts (extractor, bolt hardware, etc.), but I haven't been able to find the Colt equivalent. Does Colt sell such a prepackaged kit? If not, I'd be interested in recommendations for what should be kept in such a kit. If I put one together myself from individual parts and repair items, what should I include? Remember, this is for emergency field fixes. Thanks for your comments.

Buying only Colt replacement parts will be substantially more expensive and they will be not as easy to locate.  Also, it can be argued that you gain nothing by doing so.  Anyway, brownells.com stocks many Colt parts.  You can also try sawlesales.com.  Neither place has the parts in kit form, but you could piece something together.  

I usually recommend something like the DPMS Field Repair Kit, stock #231-015-003 at Brownells(Contains one each: hammer spring, trigger spring, extractor, extractor return spring, firing pin, ejector pin, ejector, firing pin retaining pin, disconnector spring.)

You stated you have a Colt preban, but you did not say if it had std size hammer and trigger pins or it has the large? Bushmaster sells both sizes, as does DPMS, so either size you can get replacement parts. If you want factory Colt parts then try R-Guns for the large pins. The std size pin parts might take you a little longer especialy if you have a real early Colt SP-1 lower.

Get a field repair kit from BM.  But then stock up on the more delicate parts of the system.

It seems to me that the bolt and carrier assembly contains the most likely candidates for breakage in a way that will shut down your rifle.  You're done shooting if any of those tiny parts break or disappear, and they're stressed with every shot.

They're mostly cheap, so I'd have at least 2 of each on hand:
extractor, spring, insert, and retaining pin
firing pin
firing pin retaining pin
cam pin
carrier key (maybe just one), with screws

Heck, maybe just buy a complete bolt assembly too, they're only $50, but make sure to get a field headspace gauge to verify safe headspace if the time comes to drop it in.

As for being hung up on Colt parts, I don't think you should worry about that (unless you NEED colt-specific fire control parts). I can understand someone wanting their rifle to be all-Colt, but for spare SHTF parts, use that cash you'd save to buy more parts instead of spending more on the Colt name.

Colt is less concerned with keeping their rifles all Colt than you are!  They buy many of the small parts from the same sub contractors as everyone else.  I once bought a new Colt that had another brand carrier.  Where there is usually a "C" stamped into the carrier there was simply a grinder mark where they ground off whatever maker's initial was there.