I assume the number is a typo. The 629 Burlington has a red frame. The 628 Northern Pacific has a yellow frame (and B&O 626).
Any 'generic' yellow will be close. A medium shade and gloss will work. From a rattle can will work well if you have the frame striped down to bare metal. A Testors or similar brand medium yellow will be very close match in a spray can. Model railroad colors will dry flat, so you don't want to use them. Needs to be Enamel, not water based paint.