In the game, there's an armor set called Linwe's set, which can be disenchanted to learn upgraded versions of four enchantments ("fortify one handed", "fortify archery", etc. all with unique names starting with "Shadow"). However, when you try to enchant with them, they normally can't be assigned to any items.

Since Skyrim released, some people have claimed that for some reason they got away with putting a shadow enchant on an item. Today at about 3:40 AM PST I went to enchant some jewelry and saw they were lit up for me as well. I ended up able to craft a silver sapphire necklace that gave over 110% to One Handed (thanks to extra effect) before stepping away from the enchanter. When I came back a few seconds later, they were grey again.

Woe is me, after about ten minutes of reloading my autosave of entering dragonsreach and trying to duplicate it, I turned the game off and on to see if a reset would help. It did not, and now I can't use PS4 share to retrieve the footage due to closing out of the game.

I'm not sure the shadow enchants are bugs. There was a bug where learning one before the weaker version (such as learning Shadowstrike before Fortify One Handed) would make the weaker version impossible to learn for the rest of the game, and that was patched. Yet the patch didn't remove the enchants, which is odd. And so is the fact that such a bug wouldn't be removed after Skyrim being out over half a decade. Plus, they even have their own unique enchantment names (and why would Bethes do that when every other unique armor set in the game, disenchantable or not, all use generic enchantments?). Are they not bugs and you can only use them at a certain time of day or some odd circumstance? Regardless of their status as a glitch, I can verify that the claims of being able to use them are true.

I'm going to keep trying to get them lit up again, and will provide a video if I succeed. In the meantime, if this interests anyone else, feel free to mess around with it too and report here if you get it to work. More people attempting this and providing videos could help us learn the method to enchant with them and everyone could duplicate it.

(Getting Linwe's set is easy. Go to the Thieves guild and ask for work from Vex and Devin (the small jobs that take a minute, each). Only take jobs in Windhelm and complete five. After that, Devin will give you a restoration quest in Windhelm. The person you're assigned to kill is carrying the armor and it can be looted from his corpse. If you haven't already, it takes twelve minutes, tops.)