Headshots are all about representing you, so when it comes to your skin you need it to show the tone it will be 95% of the year, so avoid sunbathing too much if you're going on holiday before headshots.
Do not hide your skin’s personality! Flaunt your freckles. Show your scars. They are a part of what makes you unique. Unique features are what makes you stand out and makes casting directors sit up and take notice.
Try to avoid wearing fake tan for a shoot, it never looks 100% natural and can come out a strange orange tone on the camera.
Think about how you normally look with regards to skin and colouring and embrace your natural tones!