GWR Goods Shed Ridge Tiles

[animotion]

I am building a GWR goods shed for Pencader station and would like to know what would have been the likely colour of the ridge tiles. From the black and white photographic evidence I have seen I am guessing that they would have been engineering brick grey but from a black and white photo it is sometimes hard to tell. And as for the pattern would they have been plain angled or capped angle. I will be 3D printing these with a roll top pattern to make them stand out but maybe the GWR wouldn’t have gone to such lengths and I can change the pattern if need be. If anyone can cast any light on this matter it would be most welcomed.