colours
The large retail outlets only ever seemed to stock red, as did most independent stores, but us in the independent market could always order any colour if we chose to. Numatic always had a flagship colour for each model, such as Henry in red and Charles in blue. Making the tubs in different colours was not the cost prohibitive part, as all tubs could fit any cleaner head for that size tub, but having the main head (the part with the motor) with colour matched lettering was, as it limited the number of colours it could be fitted to.
It was more expensive this way as Numatic had to run four different production runs (one for each colour), meaning four production lines, or at least a break for the operator to change the colour of the ink in the printing machine. With white lettering the main head could be attached to any colour of tub further down the assembly line, and left the operators free to roll out the same style head one after the other.