Greetings Dennis! Thanks for posting this question, as I see it as part of the overall strategy in helping users reduce the ‘security friction’ the world requires today.
Similar to your request, the latest release does support ‘light branding’, and allows you to upload a light and dark mode, as well as a mobile light and dark mode images.
The following Community announcement provides additional information on the release: Minor Version 9.3.0 Released
Maurice