That sounds like an "emperor's new clothes" question 
Looking on google it seems that 'restored' machines are often red and pink, but preserved, unrestored, ones are either pink (with red bits underneath).
The one at Pitstone does look redder on the framing, but I suspect it's because the paint has weathered differently on the different timbers.

I also found a few examples of an American machine where the paint has flaked off the metal (galvanised) panels and an old coloured engraving where the frame is red but the panelling is natural 'wood'.
I did a google image search of the engraving and google suggested:
"Best guess for this image: herd of sheep under trees"
Neil
Edited By Neil Wyatt on 04/08/2018 18:13:11