The P.P. are a culture of their own. Every one of them has a different color and every colony strive for color unity. The collect small items that connects the colors between the clan members - if there are just a bright red and a bright yellow one, they will both go for orange objects. The red one for more red-orange, the yellow one for more yellow-orange. They are annoying - on the level of Borstels. They make small objects vanish. By the objects you can tell, which colors are dominant in the colony.
How to fight it
A sad way would to paint everything you own grey and set a trap around a box of crayons. I usually just let them fare. They are not dangerous.gab