Quote from Esileruf;1286008:
Is it possible to find out via the code what the possible colors for an item can be in an NPC shop. i.e., Wood items such as ladles, cooking tables, and fire wands ever not being their browns and what would be the chance of it?
Palettes are in /data/color/ in the client and generally named properly.
For example here's cloth.raw which is the normal cloth junk.
[Image: http://i.imgur.com/4CGTBcb.png]
And cloth_bright.raw for whatever else, or "Northern Lights" as people call it?
[Image: http://i.imgur.com/wqhxvi7.png]
I think silk.raw is used for nylon stuff?
[Image: http://i.imgur.com/HtzhsQr.png]
Obvious what leather.raw is for.
[Image: http://i.imgur.com/jZGbGFP.png]
They're 24-bit and most of them are 256x256 (if you want to open them in Irfanview and see for yourself), though some of them are just a few pixels, things like gold and bread. Older things that always have a fixed color on them tend to pull from a fixed palette, like there's a separate palette for meat items so they always look red no matter what they're dyed.
Like these examples, the colors are just the leftmost pixels.
Meat...
[Image: http://i.imgur.com/Fu2F4e0.png]
Cheese...
[Image: http://i.imgur.com/phSJGoS.png]
Wood...
[Image: http://i.imgur.com/PtaKQ6K.png]
Looks like there's really only 4 pixels or so for wood, so items that use this palette will never show up with any other colors under normal generation rules. Only ones that come from events and gachas and other scripts that actively choose to generate them with specific colors or something.
Note that this is a different concept from items that happen to be generated with specific colors every time. Like "Black Angel Wings" and "White Angel Wings" are actually recolorable and use the cloth palette, they can be generated with different colors on Aura for example. But all of the methods that generate them in-game in NA set them to specific colors and they can't have dye items used on them so the only ones you'll see on NA servers are black/white unless a GM manually generates a special pair (like those pink tiny guardian wings).
So anyways the main answer for how common it'll be for items to come out with rare colors depends on the color palette they use, assuming you're only talking about ones generated from normal drops and NPCs.
(Some dungeons can generate items with specific colors not normally obtainable but people haven't cared about that stuff since like G7.)