The prefers-color-scheme CSS media feature could be a way of doing this without requiring any additional action from the user. The spec is still a draft but it

The prefers-color-scheme CSS media feature could be a way of doing this without requiring any additional action from the user. The spec is still a draft but it has decent browser support. https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme https://developer.mozilla.org/en-US/docs/Web/CSS/@media/pref...