Thomas thee blue train works all day while Percy the green train works all night. Told in the simplest language, here is a charming tale of what they each do. Perfect?and portable?for toddlers and their caregivers.Thomas thee blue train works all day while Percy the green train works all night. Told in the simplest language, here is a charming tale of what they each do. Perfect?and portable?for toddlers and their caregivers.