Banners darken when a tooltip is displayed.
1) Place a banner
2) Open inventory
3) Mouse over any item
4) The banner darkens
Here are some screenshots of the bug. The first one is a banner without any tooltips showing.
It's barely noticeable on the screenshots but ingame the difference is quite obvious.
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[media][media][media][media]

Probably duplicate of MC-51298

Resolved as of 14w31a

not for me