Upon opening the ‘print’ dialog in Preview.app today, I noticed this button near the bottom:
A standard Aqua button, but yellow. I’ve never seen this before. My printer is low on yellow ink, so maybe the button changes color depending on what ink is low? That is very cool.
Nope, it’s just the color Mac makes aqua buttons when one links to a specific URL, I believe, possibly only when it links to an apple URL. I don’t think it has to do with the ink color.
By the way, it’s natively defined in /System/Library/PrivateFrameworks/CoreUI.framework/Versions/A/Resources/UI.bundle/Contents/yellowmaterial.png