Pretty nice job! It's really good actually, but I thought I might just throw out some tips:

• This is actually just personal preference, but in your cheat sheet, you have Glyphs, then Marks, then Quints, then Seals. It's just that typically it's in the order Marks->Seals->Glyphs->Quints.
• Based on your core items, you've already shot past the 40% CDR cap. You have 45%, and then you have the 5% from your masteries. In essence, you wasted gold on an extra 10% CDR, and that gold can easily be used elsewhere. I personally like running Mobility Boots on supports, as it'll allow you to run everywhere and ward, but on Lux I figure Sorcerer's Shoes are a better choice.
• This brings me to my next point. I agree with Maintained, that Lux should be built with damage, other than utility. There is a reason as to why Lux is played as an APC, and that reason is that her AP ratios are pretty freakin' amazing. Lux isn't tanky at all, so Locket of the Iron Solari is pretty useless with only the 300 extra health. I think Mikael's Blessing is a situational item, unless the enemy team has a lot of CC, like Leona or Thresh.
• If you build AP, your shield will be more powerful anyway, and during teamfights, you can barrier up to twice the amount. Think about it this way: Your tank initiates, and you toss your wand across your entire team. Then, everyone takes damage and your shield is broken. Then your wand returns, and you REbarrier them. All in all, you can force the enemy team to cut through a lot more "health" and you'll be able to benefit your team about the same, if not more, than Locket.
• Yes, Lux has a lot of utility, and that's what makes her a viable support. However, keep in mind that all of your CC abilities also deal damage. Besides, you can just become a second AP carry for your team. I don't think Lux is a pure utility support like Lulu or Sona or Soraka (all of which coincidentally have poo ratios :/)
• Have you considered switching out your Stealth Ward for a Sweeping Lens? Although you can upgrade your Warding Totem to a Pink ward, with Sweeping Lens, you can clear wards every 60 seconds. This is especially useful when grabbing a quick Dragon or whatever. You can always buy Pinks and since they're "permanent" you shouldn't have to worry about them running out so long as you put them in a safe spot.
• In your items section, I think you might have miscoded the "Captain" enchantment.

To be honest, I only said this much because I was honestly impressed ^_^ I don't have much time nowadays to comment this long, so you better feel honored ;D Haha, jkjk. but really nice use of codings and your pictures were really nice as well. I just hope I provided some insight on what I think might be other viable choices. Awesome job, and keep up the good work! +1

Good guide! You explained your choices reasonably well and your coding isn't bad at all. I will test this build out when I play support Lux for sure; I always did love playing her as one :).

However there are some things I would like to address...

1. The guide overall lacks key parts (in my opinion) to a complete guide. One being gameplay; laning information is generally useful and a teamfight explanation for support Lux would help people out a ton!
2. You could add alternatives to your masteries, runes, and such.
3. You could add some tips on using her abilities.
4. A good additional section to add would probably be a "When and When Not to Pick Support Lux" or something like that.

Annie only has a stun for her utility.

Lux has a slow, stun, scout and shield in her utility.

I believe the only reason people use Annie support is because they want to do damage and get kills during mid and late game, a proper support doesn't really need to get any kills unless certain situations arise (for example Lux's Final Spark can be used to kill enemies that are just out of reach).

I personally think Support Lux should be played like Support Annie.

Probably because Lux doesn't have enough features to make her viable with mostly utility. That is only my opinion though. I don't really know because I don't play support at all.