There's some huge pallet company, who's name escapes me, but they own every blue/red pallet. That's why you see HGVs on the motorway with coloured pallets on. They then lend them to companies, who pay a renting charge then they send them back. Like LoveFilm, except with pallets!
So nobody will let you have coloured pallets because they have to pay if they break/lose/give them to trials riders.