I read this book in the 1980s.
Book features a long necked dinosaur skeleton in a museum. A child tries to feed the dinosaur food but it keeps dropping out of his bones. He then fills the dinosaur skeleton with coloured balloons.
Please help I loved this book
I remember this too… but I cannot Google-Fu a title! Just thought I’d add, based on your spelling of “coloured” and my being from Toronto, that this might be a Canadian or UK book. (Slight chance it was an animated segment on a show, unless you definitely remember it being a book.)
It is listed as one of the stories in a collection in the book called Sounds after Dark written by Bill Martin