It depends on the species and individual somewhat. I believe there are forms of albomarginata, reinwardtiana, ventricosa and mikei that have reddish pitchers/leaves/stems in good lighting (and other species for sure - those are just off the top of my head.) I have a number of plants that are purple or bright pink under bright lights, and seem to love it. You could also take a look at the pictures on http://www.nepenthesaroundthehouse.com/; that guy grows his Neps outdoors in California. There are certainly some that prefer partial shade, but the coloration is more than just "sunburn."
I think that hardened Neps (IE grown as houseplants as opposed to terrarium subjects) probably manifest coloration more readily ones grown in more generous accommodations. Terrarium-grown plants commonly have more delicate foliage in general and this correlates with sensitivity to watering and the condition of the air; it wouldn't surprise me if the same were true of light. Thinner leaves are at greater stress from direct exposure to sunlight, so they probably often do get genuine sunburns. Pigmentation is probably just another part of the hardening response in some plants.
Nice pics Matt - I'm drooly (hehe, your avatar probably is too.) I had a hamata come to me in a similar way but mine kicked the bucket after idling for a year and never really settling in. Oh, what could have been...
o//~ Livin' like a bug ain't easy / My old clothes don't seem to fit me /
I got little tiny bug feet / I don't really know what bugs eat /
Don't want no one steppin' on me / Now I'm sympathizin' with fleas /
Livin' like a bug ain't easy / Livin' like a bug ain't easy... o//~
As long as the leaves are succulent with pigmentation I think that's great, his plant just shows a healthy red blush. When it gets too dry and the leaves get a crispy burn (not succulent but dry like autumn leaves) or red in spots and splotches that's not good pigmentation. What I'd call stress pigmentation is where it looks like someone bled all over a plant and some of those red spots were dark or cripsy. But an even blushing like that is good, it let's you know the plant is getting adequate light and in general strong light helps give you the best possible pitchers as far as size and color. Some Neps don't blush red but yellow, pink or purple. I think it was my old N. burbidgeae which turned almost totally purple at first and then just had a violet blush thereafter on all the new leaves once it settled in. We need to have Av8tor post a link to his hamata, I think it's entirely maroon, or was at one time.
N. hamata was one of my faves, those teeth, the scraggly hairs and never getting too big so I could keep the thing unlike bicals and so on who outgrow even the biggest chambers. Mine grew really good and fast, within about 3-4 years becoming a double vine. I'm hoping to get one again once I get my new HL setup built. Seems the cool Neps were easier to get years ago, nowadays they must be fashionable or something cos the prices are insane stateside. The new Gucci Nepenthes are in!
I guess you won't see Av8tor1's hamata driving a prius! Figures with such a viscous plant :P