Here is a van in Crimson.
https://www.google.com/imgres?imgurl=https%3A%2F%2Fwww.bluebell-railway.co.uk%2Fbluebell%2Fpic2%2Fvans%2F2531_jackgregory_28dec21h.jpg&imgrefurl=https%3A%2F%2Fwww.bluebell-railway.co.uk%2Fbluebell%2Fpic2%2F2531.html&tbnid=HvJ-gtKg3n9trM&vet=12ahUKEwjUoOyk3LT3AhVghXIEHUJVCmIQMygjegUIARCKAg..i&docid=lc583CfSCo7FTM&w=1920&h=1250&q=sr cct utility van&ved=2ahUKEwjUoOyk3LT3AhVghXIEHUJVCmIQMygjegUIARCKAg
No idea if any were ever transferred out of the SR they did get around and could be seen at all ends of the country.
The odd thing is that I used to live close to the Bricklayers Arms in South London and in the late 70s it was a Parcels Depot. I remember seeing ex SR vans of all sorts and BR Mk1 GUV, BG, BSK and CCT of different types. As for livery, the Mk1 types were Blue/Grey or Blue with much dirt but the SR Vans were that dirty I wouldn't be able to guess at a colour.