Good stuff. In 3M products, green is the most course. Then maroon. Or brown. Then gray, then white. White is the finest and can very handy for polishing.

I use gray on my rims. Or the previously mentioned sandflex blocks. What's good about them is not that they are better abrasives, or that they are impregnated rubber, but that they offer a flat surface so you only do the sidewall without danger of going over the polished surface inside the rim or touching the tire. Very quick and easy to use. And it removes hardly any material at all. No need to imagine heavy handedness. Just a quick spin with the thing and you're done. And no stinky and dangerous brake fluid to deal with.