They can't be seen in-game due to camera constraints, but the tree top tiles visible at the base of this map aren't a mapping error; they are in fact part of the level's layout.
The high-up, strangely coloured barrel near the end of this map is an example of a 'bonus return barrel'. These barrels, which are positioned throughout DKC's levels, blast the Kongs back into the level upon exiting certain bonus areas. These barrels are never meant to be visible, and have no colour palette assigned.
creaothceann, Simion32, Cody, Stone, Kingizor, Blaziken257, Tompa, Raccoon Sam, and everyone else who has helped over the years!