Do foreign women need to cover their hair in Sri Lanka?

No, foreign women do not have to cover their hair in Sri Lanka for everyday activities, because there is no cultural or legal rule that forces this in public spaces.

The only exception comes up when entering mosques, where women visitors are expected to cover their heads with a scarf. When going to Buddhist and Hindu temples, hair covering is not required, and in some Hindu kovils you might even be asked to tie your hair back. Still, modest clothing rules for shoulders and knees are strictly enforced for everyone, even if the hair itself is left uncovered.