[Peter Clare]

I well recall Reckitts Blue being used on washing day, usually on a Monday.

I believe that the colour you are looking for is Sky or Azure, (under surface colouring) this information is taken from AMO A.664/42 to AMO A.1246/43 Camouflage Colouring and Markings of Aircraft, the section dealing with day fighters abroad.

Regards
Peter Clare