Notification action icons may have the wrong color on desktop. For native Android apps it is recommended to use flat white icons, and this guidelines transfers well to Chrome on Android. Chrome on Android performs some processing: it ensures they are white, and presents them with a grey color filter in the Material theme.
On Desktop, we currently don't do any processing of the icon colors. There are also no guidelines that I know of. However, specifying a white icon like for Android makes the icon basically invisible as it is a white icon on a white background, see screenshot.
The attached screenshot also shows what would happen if we painted the icons grey, in which case important information may be lost.
Neither approach seems perfect, but I wanted to at least track this issue clearly.