I've seen some pictures of purple-tinged uppers from GM and/or H&R, but this one is
(a) really purple
(b) has no flash on the rear strap and
(c) shows little in the way of use or wear.

So, the question is, did anybody, i.e., OEM or government contractor, ever produce any like this?

I suspect it's just a bad aftermarket anodizing job because even though purple hanguard rings slipped by, I doubt this would.
Also, I notice the A2 ejection door.

I have seen purple and brown uppers and they all were replacement uppers. I have seen a select few that would pass for 603 uppers without forge codes under the rear sight. The photos were not good enough to see proof marks forward of tbe ejection port so I was not sure if they were Colts or not.

Others who know GM parts might have more strong opinions. There is an upper like you describe for sale elsewhere and at first glance I assumed it was a Colt, but in my 40 years of collecting, I have never seen a Colt that purple.

Your pic did not post BTW.

Yes, but they don't do it on purpose.
In the early 90's I had a Colt 9mm upper that was very purple.

We have a member (I think it was SomeBob) that built a rifle from these purple parts. Im sure he will be around to post.  from what I understand it is an unintended affect during Ano. I have seen it on some of the Knights RAS systems along with a bunch of A2 uppers in the past. 

When I was in the service, we ended up with a whole shipment of A2 replacement upper from the supply depot in the states and they were all purple!

I've had purplish ones from Fulton as well as Olympic Arms.  Haven't seen one for awhile, though.

Yeah, it didn't post because I forgot to post it.
Here ya go:

does it have the auto sear relief cut? that old anodize would strip easy lol.

Yep, that is the same upper I saw for sale. I am unable to see any proof marks forward of the ejection port due to the photo. They may in fact be there. The port door is wrong.

I have serious doubts it is a Colt unless the proofs are faint. But apparently there were some GI replacement uppers that were in fact purple. So, I doubt I helped that much.

Well I said "anyone" because I suspected something like this might have slipped in somewhere along the way.
If anyone knows more about purple replacements, I'd like to hear about it.

If such are known to exist, that might mean this wasn't some kind of aftermarket botch-job.

Anybody have any solid info to contribute?

Its possible that factory seconds made it to early ar15 manufacturers, and they were anodized commercially. If you can find proof marks that would narrow it down. But otherwise a part of that age has prob seen many hands.

Looks like my Sendra.

I believe most purple A1 uppers are made by LM (LAR/Martin Marietta).  There may have been others as well, from my understanding it was made for the military as replacement uppers and are good uppers.  I would love to have a couple of the purple ones myself.  Instead of stripping/painting or redoing it I would just leave it be as purple.  You can go find a black/grey one any day of the week but it is very rare you see purple ones.  I would personally pay more for one if I was in the market when looking.  That picture you posted is the most purple one I have ever seen, but it could just be the lighting.  Usually they have just a slight purple hue to them that is noticable but doesn't stand out as much as that one.  

One odd thing I noticed the other day when installing a barrel on a new Aero A3 upper - the barrel nut did not align correctly so I stoned the front of the receiver to just take a slight bit of finish off to get it aligned correctly only to see that the stone I was using had purple coloring all over it.  I am not sure if this is common or not, you don't really hear of any of them having a purple hue to them and mine certainly doesn't it is very matte black like most others.  I've had to do the same thing on a BCM upper before and don't remember the purple coloring coming off but perhaps I just didn't pay attention to it.

Good point about the LM coded replacement uppers. I have owned 3 in my buying and collecting times and all turned purple to some degree when exposed to oil or lube. But all had the LM code under the rear sight wheel.

As to Sondra being the maker of the upper in the pic, I have seen several of them too and all where very dark grey or black. Others may have a different experience.