Uniform
Coincidental clothing.
Go out looking for people in the same colour or clothing who don't know each other. Two people in the same shade of orange. Three people in navy blue in the same frame by accident.
How to shoot it: This is a hunting project, so go out looking for accidental colour matches between strangers, two people in the same orange, three in navy by chance. Frame wide enough to hold both and shoot fast, because these line up for a second and break. Busy pavements and crossings give you the most rolls of the dice. Shoot in colour and let the rhyme carry the frame.
The output: Colour-led and quietly funny.
Any.
Find two strangers wearing the same colour. Photograph them in the same frame.