Code switch indicators in FL materials are only needed when context and format are not sufficient to let the reader know of a shift in language. They are rarely used. In most FL materials, difference of typeforms, inserting a colon, or indentations in format are enough. In cases where they are not, follow these guidelines as prescribed in The Rules of UEB, Section 14.2 and 14.3.
Let me know if you need more specifics! If you attach a pdf, I would be able to help more.