When an appearance is collected, but not from this item, the text was usually always blue in SL versions of the addon.
Ever since DF versions of this addon there is an inconsistency where it's switching between green and blue, see screenshots below.

https://i.imgur.com/9zA4wWD.png
https://i.imgur.com/Cpgbpxb.png

Both items from the same boss, King Rastakhan in Battle of Dazar'alor mythic.

Additionally, I just got this item: https://i.imgur.com/VNqUVQW.png
And tooltip says: https://i.imgur.com/sk0jAGX.png