Hello, I just happened to run across a reference to this in the GW2 site forums, and wanted to raise awareness. The following can be found on Arenanet's GW2 website's settings tab, (account.arena.net/settings).
"Guild Wars 2: Limited Time Exclusive Gift
If you're subscribed to our newsletters as of April 29, 2019, you will receive an exclusive Glowing Purple Mask skin.* Only available to subscribers, this in-game cosmetic item will give your Guild Wars 2 character mysterious, glowing purple eyes when applied to a piece of head armor.
Edit your newsletter preferences below to be eligible for the gift.
Allow 8 weeks after April 29, 2019 for this item to be distributed."
If you've never gone there before, go to www.guildwars2.com, then login (upper right hand of screen, by default same login/pass info as your game account's), then the settings tab.
According to what I read on other forum threads, you need to be signed up for all 3 newsletters to get the skin, and saving the settings has been a little twitchy for some. Turning them all on (green coloring) and saving preferences did NOT keep the settings for some reason, so I'd advise going through the process of confirming through the email they're supposed to send out. I myself turned them all off, then back on again, and did NOT get the confirmation email. Toggling them a 2nd time did work, sending the email and keeping my settings turned to on.