Oh my goodness, just LOOK at the hair on that pony on the right! *swoon*
Yes, the one on the left is faded.
You can't go off whether the pony has other types of damage because that pink hair can fade
very fast. I've purposely faded G3s (for customs) in only a few days--and I mean totally faded, from factory-pink to pure white.
You also can't go by the roots . . . I took the head off of a G3 Minty that I faded and even the roots on the inside of his head had turned white. I guess mean ol' Mr. Sun blasted right through the plastic.
I can actually see a bit of a tint left on the pony on the left . . . I do find that previously-pink hair sometimes shows a bit of a sheen in pictures, even when it looks whitey-white-white in real life.
IMO part of the reasons there are "variations" of fading pink in the package is that it just fades so easily. If a pony was exposed to sunlight, even briefly, even in the store, even when the box is being unloaded, even
in the factory itself, that hair is going to start to fade. And who knows how this hair was stored. I'm sure none of the factory employees knew that it would fade, so they wouldn't take precautions against that.
So basically I think the "strong" pink, like on the righthand Curly Locks, is the "truest" shade, but what with one thing and another almost every pony with that shade of hair ended up being faded at least slightly.
Edit: Although now that I think about it, G3 had at least two shades of fading hair--one seen on curly-haired, all-pink-hair Minty and a stronger pink seen on straight-haired, white-and-pink striped Minty. I still feel it's likely that all G1 ponies started out with the same shade of pink hair, though.