The light gray glass pane is invisible in the inventory [Creative Tab and Hotbar when inventory open].
In my hotbar when I play (and don't show the inventory, there is no problem [hotbar2]
MC-50375
Light gray glass pane invisible in inventory
Resolved
Duplicate
0
Joshua S
(Unassigned)
Unconfirmed
Minecraft 14w08a, Minecraft 14w10b
Retrieved
I think you should reopen this ticket (or the other one). We should be able to distinguish at least block outlines.