One of our employees currently has an extreme hair colour which goes against our strict dress code. The Headteacher asked me to relay this to the member of staff and explain that this will need to be changed to a more natural colour as soon as possible. However when I relayed this message to the employee they instantly became defensive and told me that they would be handing in their notice. The employee claims they weren't told about this at interview but I went back through my email trail and the dress code was sent to them when they first started so they were aware of the rules. How would you approach a situation like this and how would you deliver this message to try and ease the conflict?