What does a red screen on my Iwatch 4 mean

Are you seeing a Red Exclamation mark on your Watch? If so, follow the instructions here: https://support.apple.com/en-us/HT204776

If you’re seeing a red charger or lightning bolt on the screen, see these instructions: https://support.apple.com/en-us/HT204640

I would suggest you call your local Apple Store and have it examined. As this is new Watch and is still under warranty.