I prefer a light theme and currently use “Tempo Light Monospace” but this issue applies to the built in light themes too. Manly I use an external keyboard and have to use foreign characters from time to time. A long press on a key brings up a list of available characters and a number (to use to select the specific character). Using a light theme this pop up list has a white background, gray numbers and white characters which means it can’t be used.
I would be happy to modify a light theme if someone could identify this list and where to find it in the theme builder.
My guess is you are using a light theme while your device is set to dark mode?
This is not an avoidable issue in this scenario, because the accented letter popup is a system element and is drawn by the OS to match the OS’s current theme mode. It best to have Drafts set to use the “system” theme to align with the current dark/light mode of the system and select appropriate themes for each mode in such cases.
I do feel like should be consider an OS bug, because Apple should take into account the visibility of the elements of that popup when drawing it, but they do not, as the match the style of the underlying control - which does not work out so well if you have selected a theme that is not consistent with the system’s.