Bedford/Vauxhall factory Bedford S Type Info Wanted

Can any one help with reg numbers and colour scheme of two special tractors used by Bedford/Vauxhall between the Luton and Dunstable sites,
Both based on Bedford S Types but converted by ML Douglas to pull an eagle solid tyred trailer to carry machine dies.
They were basically tractor units with flat bed fitted and one I believe had orange and black diagonal warning markings on the cab nose,but can,t find what colour the truck and trailer were.
Any help would be greatly appreciated