Firefox already supports separate light and dark app icons on macOS, but the current “light” icon still uses a relatively dark purple background. As a result, Firefox visually stands out in a light macOS Dock instead of integrating with the surrounding applications.
This is particularly puzzling because Firefox on iOS and iPadOS already has a clearly light default icon that fits the platform much better.
Bug 1997245 shows that Firefox for macOS originally also had a white light variant. Mozilla deliberately replaced it with purple because the white background was considered to provide insufficient contrast with the Firefox logo. I think that trade-off is wrong from a platform-integration perspective.
The Firefox logo clearly works on a light background on iOS and iPadOS. On macOS, the current purple “light” icon attracts unnecessary visual attention in the Dock and makes Firefox feel less native than Safari and other well-integrated Mac applications.
Please either:
Firefox is exceptionally configurable in much more consequential areas. It would be strange for something as constantly visible as the Dock icon to remain an unavoidable branding choice when Mozilla already has suitable alternative assets.