Currently, the Surface color defined in the theming repo for the Fluent theme is almost the same as Grays.50 in Dark mode and Grays.900 in Light mode (it looks the same; the difference is only in the hex/rgb/etc.).
Some components use these Grays as backgrounds in Dark mode for their states, so it is hardly noticeable that you interact with them (Check the Dialog component and Date Picker/Action Buttons in Dark mode for reference).
Our suggestion is to change the Surface color
from ->to ->
We've already checked where this Surface color is used in the Theming repo, and as far as we can see, the only value used in the repo is Surface or Surface 500. In some places, the color style is used with additional opacity, but we believe this will not cause any problems.
Currently, the Surface color defined in the theming repo for the Fluent theme is almost the same as Grays.50 in Dark mode and Grays.900 in Light mode (it looks the same; the difference is only in the hex/rgb/etc.).
Some components use these Grays as backgrounds in Dark mode for their states, so it is hardly noticeable that you interact with them (Check the Dialog component and Date Picker/Action Buttons in Dark mode for reference).
Our suggestion is to change the Surface color from ->
to -> 
We've already checked where this Surface color is used in the Theming repo, and as far as we can see, the only value used in the repo is Surface or Surface 500. In some places, the color style is used with additional opacity, but we believe this will not cause any problems.