RAF Emergency Set (K6 Crash Tender)
Airfix's imaginary crash tender!

By all accounts, this crash tender never existed, and certainly not in WW2 in red.
During WW2, Dagenham's Fordson WOT1 was the crash tender of choice (with a body that looked much like this one - the chassis and cab would be completely different though - and I've read that even that body didn't appear until the very end of WW2), and usually in camo colours as bright red tends to make the airfield a bit noticeable to the Luftwaffe - red wasn't used until after the war.
An Austin K6 emergency vehicle did pop up toward the end of WW2, but it was a CO2 tender (the only one), not a foam sprayer and looked a lot different.
So all bets are off regarding "authentic colours": I'm definitely not using red (one of the nightmare colours to paint, along with yellow and white!).

(Having first sweated then enjoyed the Refuelling set recently, I am clearly a glutton for punishment...)