Already Known?
https://www.curseforge.com/wow/addons/alreadyknown
Puts green, blue, yellow, cyan or purple tint on already known scrolls/pets/other learnable items on vendors and AH.
Simple and small addon to color already known items on vendor and AH frames. Works at least on profession designs/patterns/etc, garrison plans, toys, mounts, pets and equipment blueprints.
Default color is green, but try /alreadyknown or /ak ingame to change the tint color.
Known issues:
Designs/patterns/etc of already known companion pets/mounts are shown as known even if they aren'tFixed in 1.12!- Quest based items (like equipment blueprints) - at the moment at least - has to be hard coded into addon, please let me know if you run into yet unsupported quest items sold by vendors.