The absolute minimum interval you should put between two hair coloring sessions is four weeks. However, the actual recommended time is around six to seven weeks. Generally, those with weak hair should wait longer, but if those with stronger hair can re-dye after five weeks.
Coloring and dyeing are stressful events for your hair, and they are potentially harmful if your hair is too unhealthy or the dye is too strong. Dyed hair requires proper maintenance. Apply conditioner to your hair every few days after dyeing to help it recover. If you foresee that you'll only wear a certain color for a few weeks, choose a semi-permanent dye that can be washed out when the need arises.