Cobba, I have a VK1A David brown and it is painted blue; done by the last owner.
When I bought my Allis B it was painted olive drab and so many guys told me that the Army used this model so it was obviously an ex-army tractor. (I can't imagine what the Army would use a 23hp, light weight tractor for in 1938). Turned out that the colour was a blend of all the left over paint the previous owner had when he painted the house.
When I stripped it down to bare metal, the first colour paint on it was iridescent purple, so I suppose it was first owned by a rock band.