I use the white ones they are softer, in fact it is what I use to clean my hands with.
Being by the ocean the scotch brite pads and their grades are stocked at fiberglass shops, making surfboards big deal here, in Hawaii.
Might also be @ West Marine or possibly autobody supplies:
7445 - White pad- called Light Duty Cleansing - 1200-1500 grit
7448 - Light Grey- called Ultra Fine Hand - 800 grit.
6448 - Green- called Light Duty Hand Pad - 600 grit
7447 - Maroon pad, called General Purpose Hand - 320 grit
6444 - Brown pad, called Extra Duty Hand - 240 grit
7446 - Dark Grey pad, called Blending Pad 150 grit
7440 - Tan pad, called Heavy Duty Hand Pad - 60-120
Blue Scotch-Brite is supposed to be about 1000 grit. I think this is a home owner marketing thing.