2-speed kickbacks are my favorite.
Had a blue band as a kid on my Sting Ray back in 1965, the blue band is has standard to high gear, most I believe are 28 spokes, for 20 inch wheels.
The yellow and red bands are low gear to standard, mostly for 36 spoke 26 inch wheels.
I have a yellow band on my aluminum composite Captain America Razor bike.
And red bands on my aluminum composite Alumasled bike, on my Beer bike ( beer labels covered Cleveland Welding frame), and my RRBBO3 bike the Rust Rat. Even got a late 1940s Schwinn Continential (garage sale find) that someone had replaced the wheels with S-5s with a red band. And I have 4 more for future builds. Most of these were from Schwinn Breeze and Co-ed bikes, and I laced or had laced to the wider wheels.
The green band I believe is bogus. There are no 3 speed kickback hubs to my knowledge.
Once your master the 2-speed kickback mentality (remembering which gear your in after you brake) they are great.