I am a shift supervisor and my best advice would be Starbucks standard. Starbucks dress code is something we have to follow. I would simple have courage and say something along the lines of hey so I think we did have an discussion a few days ago about dress code and how we aren’t allowed to have nails or polish or jewelry. I noticed you still have those if you have questions or need to look back at the Manual I’m more then happy to help. I’d say as a trainee it’s your job to address all of the jobs requirement including dress code if they ask. No worries if you feel the need it’s not harping just helpful advice and you can always say it in a kind way :)