What is the difference between "in red uniform" and "with red uniform"?
When are with and in used when describing someone's clothing?
"In" works well when describing a specific person or group of people in a specific setting
I met Troy Deeney in his Yellow and Red Watford kit.
"With" could be used in the trivial way, implying he is not wearing but carrying the uniform
I encountered Troy Deeney with his Yellow and Red Watford kit and 3 large suitcases
But the use of "with" I would use is when the uniform is being described as a generic attribute of the people:
In the Championship the teams with Yellow kits are Watford and Norwich
here we don't see a specific person or team in a specific situation.
If you said I saw a man with a blue uniform, I wouldn't be entirely sure as to whether he was wearing it or carrying it under his arm.
But 'in uniform' makes it perfectly clear.
'in' should be used, when referring to the dress in full. Eg. Mark is the soldier in the red uniform. 'with' is used when it is specifics. Eg. Mark is the soldier with a/the red cap.