red deisel is perfectly legal to use in any machinery you wish, providing it is not a deisel engined road vehicle, hence DERV .
the only differnce of course , as Mike quite correctly pointed out is the dye.
Numerous ways of trying to get round the task have been tried by people, including hidden tanks , mixing with additives , straining through different filters including sand but today none will work, in the days when it was just the tank was dipped you had a chance. Today a simple sensor to the exaughst they can tell instantly, wether you have it in , had it in or just happen to have a little in from months ago.
The consequences, well certainly they can impound you van.
having said that I did once put red in a small van years ago after running out on the motorway, just happened to be a kind farmer a hundred yards away

I was lucky.
geoff