A man in a blue shirt is performing a skateboarding trick near stiars while two other men watch.
Nobody has a shirt
Two men watch a man in a shirt that is performing and then we have nobody has a shirt. Even if the the men watching the skateboarder didn't have shirts on and it was a hot day, someone had a shirt.
The man either has a blue shirt  or nobody has a shirt.
If there is a man in a blue shirt, it cannot be that there is nobody with shirt.