From the Super Mario Wiki
Banana Balloons are objects found in the game Donkey Kong 64. They are balloons with a picture of a banana on them; they appear in a variety of five colors. In the game, they float through the air in several different patterns. When shot with one of Funky Kong's weapons, the Kong shooting would receive ten bananas. However, the color of the balloon must match the corresponding Kong's main character: yellow for Donkey Kong, red for Diddy Kong, blue for Lanky Kong, purple for Tiny Kong, and green for Chunky Kong. They are located in most levels of the game, and because of their flight paths, some are more difficult to find and destroy than others, with a few only reachable by using Funky Kong's Sniper Scope.