Right now the user can choose what language they want to view the OPAC/staff client in, but not which theme they want to use. It should be possible for the user to set the theme via cookie the same way language is set.
Maintaining multiple themes has been proven nearly impossible. You can still add your own, but not sure if you'd want patrons to use more than yours in that case. Maybe another approach: instead of a theme have multiple CSS files to choose from? Normal, high contrast, simplified...
(In reply to Katrin Fischer from comment #1) > Maintaining multiple themes has been proven nearly impossible. You can still > add your own, but not sure if you'd want patrons to use more than yours in > that case. > > Maybe another approach: instead of a theme have multiple CSS files to choose > from? Normal, high contrast, simplified... I feel like someone was talking about that recently. I think even that would be difficult to maintain, unfortunately.
I'll mark this duplicate with the more recent discussion on adding a dark theme or similar on bug 31327. *** This bug has been marked as a duplicate of bug 31327 ***