It's great to see this being produced; the model looks fantastic already. And even better now it's going to have the red/orange cantrail stripe applied – well done to all involved in making that happen. The news that that line will be added has confirmed that I will order one of the green ones, I now just have to decide which version!
But I've just come across a colour photo of the loco in early-BR logo green livery that clearly shows it has another thin red/orange line. Not wishing to open a further can of worms, there is clearly a fine line about a quarter of the thickness of the cantrail stripe applied across the base of the curved cab front almost immediately above the joining strip (bracing?) at the very bottom. The line parallels that bracing strip up around the side of the cab to the base of the cab door. The bracing strip itself, and maybe the angled triangular plate angle that fills the gap between the buffer-beam corner and the base of the cab front also look black to me in the photo, rather than green, though that is not definite.
The colour photo can be found in Green Diesel Days by Derek Huntriss (First edition 2005, published by Ian Allen / ISBN 9780711030664 – the one with the green 55 on the cover) and found on page 24. It shows a clean 18000 at Swindon works with a ladder leaning against its side and is credited to TB Owen and dated 18 May 1957. I've not been able to find the same photo online, but it is almost the same as the RCTS one that John Isherwood has posted/linked to in black & white – the 12th one down; it was clearly taken on the same occasion and from almost the same spot. To me, the red/orange line doesn't show in the B&W photo, but the black bracing band at the bottom of the cab does and is distinguishable from the green.
Gareth