Stop and Go Barrel
From the Super Mario Wiki
This type of barrel only appears in the level, Stop & Go Station. During this level, there are many Rock Kroc enemies dashing across the areas, and they can easily hurt the Kongs. Numerous Stop and Go Barrels are placed throughout this stage, showing the word "Go" on them. If the barrel is hit, it turns into a Stop Barrel for a short period of time. While it is a Stop Barrel, all the Rock Krocs in the area cease to move and curl up into a ball, becoming harmless. After a short time, all Stop Barrels become Go Barrels again and the Rock Krocs will resume moving.
Noticeably, when these barrels are set on the "Go" setting, the lights illuminating the level turn green. When they are put on "Stop," the lights turn red.