That would be caused by copper, either from your fill water, or from the cell in your SWG which generates a small amount of copper ions as part of the chlorination process, for it's algaestatic properties.
So says Intex, is it really necessary? I don't know, someone else will chime in and give info on that if need be.
If this (copper) gets too high, which it may have with your SWG running so much, you will get too high a concentration of copper, thus causing the green hair when it reacts with the chlorine.
You'll have to test for copper levels to see where they are at, but I'm sure it's in there, it's just a matter of how much.
As for testing, Intex should have included some copper test strips with your SWG, check the expiration date on them and follow the instructions. I know test strips are frowned upon here, as they are horribly inaccurate for FC/pH/CYA, etc.. type levels, as is true, but we do use them for salt, not sure if they are accurate enough to trust with copper. Someone else will have to chime in on this.
To reduce the copper, you can do one of the following.
A. If your fill water doesn't have copper in it, then just drain some of the existing water out of the pool and fill with fresh water, adjusting levels appropriately. How much you drain, depends on how much copper is in there. Test both the pool & fill water.
B. Use a sequestrant, which doesn't remove the copper, but it binds to it, preventing it from causing problems such as green hair.
C. Some filters will eventually pull it out of the water, but if you have the Intex cartridge filter, this likely won't happen. Some people have been successful with using rags in the skimmer basket, or skimmer sock/scum bag.
If A is true, I would go that route, as sequestrants break down over time & have to be added again. C is probably going to take quite some time, so if A doesn't hold true, then B would work temporarily while you perform C. How long C will take, I can't say, I have never dealt with metals. But trust me, someone here will now, you can count on that. :-D
As for pH itself being the cause, to my knowledge, it won't cause green hair, not on it's own, but high pH can exacerbate the effects of any copper present in the water and "activate" it if you will, so it turns blonde hair green.
As far as getting the green out of the hair, Nexxus makes a product for that, which the forum recommends and users have used with success, called Nexxus Aloe Rid Shampoo.
Also, some users have reported the "Swimmers" line of products by "Ion" sold at Sally's Beauty Supply. One is a clarifying treatment sold in a little packet, the others are conditioners, shampoos and an all in one conditioner+shampoo. All of which have been reported to work, but not sure on the conditioner alone, but the others, yes.
So lots of choices there.
As a final note, do inspect your SWG's electrolytic cell and copper cell to make sure they aren't beginning to corrode, seeing as you have been running it so much with yo-yoing water chemistry as you have worked to get it in check here on the forum and through your own hard work.
If it is built up with white or black stuff, then it's time to soak her in vinegar as per your manual's recommendations.
I have found that using a hacked down styro cup on the end of the electrolytic cell works great to seal it up, it even kinda threads on there if you twist it. This way you can stand it on end and fill her up with vinegar and let it do it's thing, without it leaking everywhere or having to use a bucket and end up using more vinegar and making a mess.
Have fun, glad you are able to start enjoying your pool again and excellent signature BTW!! :-D