The reason the color shifts at slightly different angles, and in different lighting scenarios, has to do with the density of the pixels, and from what I understand, the various treatments the panel gets to allow it to show the most neutral screen color possible.
Apparently, pure white LEDs are too expensive to mass produce. So panel manufacturers use cheaper colored ones, then try to neutralize that color with phosphors and coatings under the glass. If you've ever really looked at "white" LED Xmas lights, you'll notice they're not really pure white...they often bluish or pinkish. Also, if you compare a standard LCD TV to an LED backlit one, you'll notice the LED ones run a bit bluish or pinkish. This is especially true of Samsung TVs, which all seem to run pink.
The pink (or yellow) you see in the iPad screen is the color they add in an attempt to neutralize the bluish LEDs. When you are indoors, the backlight of the iPad is generally stronger than the ambient room light, so the effects of the pink correction are not as noticeable. But when you're in bright outdoor light, the ambient light is actually reflecting off of the color treatment, and the backlight is not strong enough to counter the reflected color you see.
The variable is the amount of treatment the panels get to counteract the base color of the LEDs. Those complaining of yellow or pink screens in all lighting conditions probably have iPads that received too much of the color correcting treatment. Those, like me, who have been complaining of blotchy multicolor panels have probably been receiving panels that did not get treated evenly enough.
As for the color shift at different angles...This is a byproduct of pixel density.
Imagine 3 people standing shoulder to shoulder, each holding a 1 foot square piece of colored cellophane. Person 1 is holding a red one. Person 2 is holding a green one. Person 3 is holding a blue one. They are collectively one RGB pixel.
Now imagine a big room, with 1024 of these groups of 3 people, all standing shoulder to shoulder, all holding red, green and blue sheets of cellophane.
Now imagine climbing to the top of a tall ladder at one edge of the room and looking down at the crowd. You can see each person, carrying each piece of cellophane, and you can easily make out the individual colors of the pieces of cellophane, even if you climb down the ladder a bit and look across the crowd.
That's the iPad 2.
Now the doors of the room open and another 1024 groups of 3 people each all file in, each carrying a piece of colored cellophane. You climb back to the top of the ladder. You can no longer make out individuals...it's just a sea of densely packed people carrying pieces of colored cellophane.
And if you climb down the ladder a bit (like tilting the screen), you can barely even see the people in the back corner. And instead of looking on to the tops of each sheet of cellophane, you're now looking into the sides of hundreds of them at once...all the colors bleed together. From the left side of the room, you see mostly red cellophane, with some green showing through. From the right side,you see mostly blue, with some green showing through.
This is the iPad 3.
