Each time you do the Intel Phase of the Cayo Perico Heist there are four guard uniforms that will spawn across 16 possible locations. They are unlikely to spawn in the same four locations each time.
You can see all of these possible locations in the video above.
You don’t have to collect all four and it depends on how many of you are attempting the heist and also how easy the uniform is to reach given the guards and cameras nearby. And of course if you’re not using the guard uniform method in the heist you don’t have to collect any.
However, it’s worth doing so as it means you can pick up secondary loot outside of the compound without being detected by guards or cameras as long as you don’t stay in their field of view for more than a few seconds.
The uniform will always be found in the same green box with a red and a white uniform, even though the actual uniform your character puts on is usually green and yellow.
The video above will show you where they are on the map.