What formatting guidelines should I follow for my bachelor's thesis if some of them are not specified by the university? I am writing my bachelor's thesis at a university of applied sciences in the Netherlands.

The university has provided me with a document outlining some of the guidelines I should follow (like what format of citations is expected and what the document should look like overall), but it does not specify anything about, for example, fonts, font sizes and color schemes. 

What is the correct approach to formatting in this case? Do things like fonts and font sizes matter very much or can I make that choice as long as it is reasonable?
I would check other submissions and ask your mentor / supervisor. In any event, I would choose a font with spacing etc. that is clear and easy to read with suitable line spacing.

Some "cursive" fonts look nice but are not "easy" for extended reading.