I Used to be Red is a rhyming magazine story.
It has been a hectic summer for Bertie. His smart paintwork is covered in dust from the roads and exhaust pipes. A passenger at the bus stop says that he thought Bertie used to be red. Thomas overhears and tells Bertie that it might be a cheeky comment, but it is true; the bus is in a terrible state. Bertie tells Thomas that he looks just as bad and he does.
So, Thomas and Bertie travel to the cleaning station where they are scrubbed with long brushes. A worker admires his handiwork now that they both look as good as new, but then he spots Henry and is sure that the big engine used to be green.