I have read in a reference book about when the Highland Railway Jones Goods was restored to steam in the Fifties and Jones’ surviving relative was present when it was unveiled in Highland Railway green.
She commented that was the wrong colour and reference was made to samples still held at the North British Loco company at that time still in business
These were steel plates with colour and lining samples painted on
From these the locomotive was repainted in the yellow scheme it carried for some years.
I do not recall which book I read this in and I have checked those I have now, so apologies for the lack of corroborating evidence.