... and Colman's were the first to use yellow as the background for the labels on their tins. This had the unfortunate consequence of convincing consumers that mustard had to be bright yellow, hence the unnecessary and supposedly harmless colouring additives found in some prepared mustards, even today. As always, check the ingredients list. You are safest with D-I-Y mustard powder in the tin from Colman's — even Taylor's, the oldest prepared brand on the market, has been recently degraded by the addition of a stabiliser, presumably for wimps who don't know how to mix in the few drops of liquid that used to form on the surface.
... and have you tried to buy sugar and sweetener free piccalilli?
Bernard C. :hb2: