As the number of downloads increases, chromium starts behaving badly

[Admini]

will it be possible to change the icon or color in custom.css if it is svg? or will it be possible to change it in the settings? in theory, if it is in a text file, like newtab or other browser pages, they can be changed in resources, which means it will be possible to display such a setting for this icon in the settings

Yes, it still can be edited in resources.pak, but it is hard to locate it.
Cusomt.css can only be used to change web pages, can't be used for the toolbar.