[ONE General] vantt1:
Possibility 2: Under-cured LOCA (Liquid Optical Clear Adhesive)

This possibility was speculated by users, and was not addressed by OnePlus. It has been said that exposing the OnePlus One's display to UV light or sunlight (apparently, 5-10 minutes in UV, 1-2 hours in sun) completes the curing process, thereby eliminating the tint. (will find sources when I have the time, it has also been said that this doesn't fix the tint/band)

Edit: might as well try the sunlight fix. I'd actually have to buy the UV lamps, and wait for them to post. Since my tint is barely noticeable, it's worth a shot. Bottoms up!

Looks like it did make a little difference! (or it might just be my mind playing tricks on me + wishful thinking)

We are assuming this is manufacturing process related ("some Ones are affected" camp). This would imply it is a QC issue, which it is not, according to OnePlus.

Samsung?

It has been noted that some Samsungs may suffer from unevenly cured LOCA. I have yet to see this for myself, but that's not to say it doesn't exist.

By design, Samsung's Super AMOLED panels have no discrete backlight; each individual pixel emits its own light. That's why dark/black images save power, and bright/white images consume more. Due to the nature of OLEDs, blue subpixels age faster than red and green, so the PenTile subpixel configuration aims to compensate for this by having twice as many (but smaller) blue subpixels than the rest. PenTile displays may exhibit a slightlu cool/blue tint as a result. An aged AMOLED display may exhibit a yellowish tint, due to the deficiency of blue.

Every generation has introduced upgrades and improvements to continually improve AMOLED tech. The Galaxy S5 and Note 4's displays finally outshine LCDs of the same class in terms of color accuracy/gamut, contrast, power efficiency, and uniformity of luminance. Sharpness has become increasingly irrelevant, thanks to the 500+ ppi of the Note 4. Any claims that LCD is objectively superior to the current generation of Samsung AMOLEDs is purely subjective. The only advantage that LCD has is its increased durability and lower price. They are less likely to fracture/crack and render the whole display useless.

I will get a phone that does not have a laminated display, and intentionally leave part of the LOCA uncured/under-cured in an attempt to replicate the tint where the backlight LEDs are.

How would this happen at the factory? I'd like to think the curing process involves a conveyor belt pizza-oven like device that "bakes" the display under UV light, but who knows!

We could ask Apple, since their iPhone 4 suffered from a similar problem :p

Update!: I think I should wear sunglasses next time.

I "only" put it in the lamp for 2 minutes, because that's how long the built-in timer is, and apparently some 20W UV lamps can fully cure a particular LOCA in a mere 6 seconds. I didn't want to risk damage to the LCD, so you could say I "chickened out"...

You can come to your own conclusions about what this means :p

In all seriousness, my One's probably not the best "poster child" for this, because I've actually heated the screen enough to separate the factory bond with the chassis, and exposed it to sunlight uninterrupted. We'll probably get more visible results by doing the curing process from scratch.

Pictured below is the phone in question; an iPhone 5S knockoff. Most of the better Chinese no-brand/knockoff phones have an OGS display (One Glass Solution), which is already laminated. It is like the OnePlus One's ToL (Touch on Lens), but not. I've posted on XDA before about it!

LOCA time!

As it turns out, the LCD is stuck to the front glass with adhesive tape all around the border. I didn't remove all of it, which resulted in some of the air bubbles to have nowhere to go :(

Get the display all clean, and apply the glue in an elongated "X" fashion:

I didn't have one of these:

So I used the phone's chassis. Bad idea. The glue leaked all over the place. The whole idea of the alignment frame thing above is to allow air bubbles and excess glue to escape, while also maintaining a uniform thickness between the glass and the LCD.

Lookin' good! This was the best I could make it. An autoclave would've came in handy.

Into the manicure UV lamp for 2 minutes. That should be inadequate enough!

The glue had already solidified enough such that air bubbles could no longer move around freely. The bubble in the top right corner became bigger, but other than that, everything went better than expected!

...or so I thought. LOCA had leaked underneath the LCD and into the backlight, because I used the chassis as the alignment frame, but it did not allow glue to escape.

The glue did not become yellow. It wasn't yellow when it was in liquid form, and I don't have much idea how long you're supposed to cure it for. Maybe it yellows further down the road?

Well, at least the properly laminated areas look great, and glare has been reduced. In hindsight, I should have used a display that could be replaced if I messed up this process.

¯\_(ツ)_/¯

This process is not going well with the Galaxy S3 display :(

If only I had gotten that $600 machine that make this process a whole lot easier (the frame laminator bit), or the lot for $4,250...