One of my colleagues in Spain sees Spanish text when accessing the the tenant but would prefer English text. Is there a way to change this as we can't see an option for it?
The UI will reference the browser's default language specification, if a supported language; if not, it will default to English. Spanish is included in the supported list.
For this user, you can look into creating a browser profile with 'en_US' specified as the default language. Referencing the tenant using that profile should then show English.