The need for recognition or somesuch

[MacMillan of Rathdown]

In screen writing clothing is rarely mentioned unless it is necessary to be shown for a specific reason...

Typically a script might look like this:

* * * * *

INT. Inside the Police Van. DAY.

Ted looks around, sees a vest with the word POLICE on the back and puts it on.

TED
(to himself)
I hope they understand this in the UK!

EXT. Looking at the Police Van. IMMEDIATELY

Ted slips out of the van wearing the Police Vest and moves through the swarm of cops without arousing suspicion. As he reaches the yellow tape at the perimeter of the crime scene a heavy hand grabs him by the shoulder. Ted turns around and looks into the face of MUSSANO, the toughest, meanest cop anyone has ever seen.

MUSSANO
You the new guy?

Ted, about to wet himself he's so frightened, nods in response.

MUSSANO
(tugging on Ted's vest)
Thought so. You new guys always wear these.

* * * * *

Here the Police Vest is described by the writer because it helps Ted escape, and it brings him into contact with another character who will become important later in the story. It also sets up Mussano, a bully, who likes to push around the new guys, and identifies them by their vests. So, in this particular scene only the vest needs to be described-- everything else is left to the creative imagination of the production team.

Once the script is turned in it's up to the production team to decide how the picture will look. The writer only supplies the necessary details, leaving things like costumes, and stage direction, and camera angles to be figured out by someone else.

(For all you film guys out there, I can't get this to format, but I'm sure you get the idea.)