You can fly during the day without the navigation lights and red strobe, subject to MEL requirements.
Since you are apparently still studying for a PPL, you might not have come across that term. MEL stands for Minimum Equipment List and is what it says. However, the average spamcan doesn't have a dedicated one, but has a list in the POH (Pilot Operating Handbook).
Look at the "Limitations" section (normally chapter 2). There should be a "kinds of operations" equipment list, which details the list of stuff that you have to have, and needs to be serviceable, for certain kinds of operations. Where "operations" is normally split into Day VFR, Night VFR and IFR.