There is a filler bondo that comes in a tube. I've seen it in green and in red. I can't find it with a "bondo" search so it is probably some other brand name. Tubes I've seen are about the size of a toothpaste tube.

1953 Chevrolet 3600
Fried Green T'mater (Vern)
In the Stovebolt Gallery
Caution: Political Statement
Man who runs in front of car gets tired, man who runs behind car gets exhausted.