The bug
Basically, the tooltips of some items no longer have their previous color. Note that this color does appear when hovering over an item while the creative search tab is selected, but not in any other contexts.
Affected text
List might be incomplete
Numbers following an enchantment name
Enchantment preview hovers in an enchantment table are no longer italic after the name (enchantment level, ". . . ?")
Banner pattern
Firework star
Firework rocket
Filled map (once a number is reached, the gray turns white)
Dyed leather armor
Shulker box content
Enchantments
Music Disc C418 track names
Linked issues
is duplicated by 16
MC-123768
Bug with enchanted books & music discs descriptions due to custom names changes
Resolved
MC-123868
Enchantment Book Enchant Text White
Resolved
MC-123877
Enchantment tooltips are wrong
Resolved
MC-123882
Potion Numbers
Resolved
MC-123909
Enchantments do not have spaces between their names and their levels
Resolved
Attachments
Comments 13
Also various appended tooltips are the wrong color, i.e. the enchantment numbers and everything after a number in map tooltip info.
I dunno if this fits under this bug or another one, but
/say hello @e[tag=XHguy]
/tellraw @a [{"selector":"@e[tag=XHguy]"}," hi"]where the entity is on a team with green color... it used to be both commands show his name in green, but now in 18w01a, the first command has name in team color, and second one does not
I can confirm these bugs.
However, in particular, I have, for example, a Bane of Arthropods book, which displays as "Bane of ArthropodsIII". This suggests that someone erased a space by accident, in a string somewhere in the code. Easy fix.
Also tooltips are colored differently in different GUIs. In the creative inventory, banner patterns are properly gray. In survival or in a crafting table, they are white.