o.k kids lets put on our thinking caps... this had to be an old late 80's I'm thinking made for TV cartoon movie... it had 3 or 4 kids red hair maybe all siblings or 2 sibs and a friend 2 older like 12-14 and a 4 year old ish any who the little kid has to paint something or gets in to the paint its green paint... gets it all over himself and I think the older kids who were soposed to be watching him have to clean it off... in the shed they find a trap door which takes them on some wild undergound adventure with a lot of caves mine carts and gnomes... maybe trolls or even dwarfs ( hey it was the 80's ) and that's all I can recall... any help would just save my brain..
Thanks

"ABC Weekend Specials" The Secret World of Og (1983) (http://www.imdb.com/title/tt0306059/)