Foam Pads:
These are glazing pads. They are also color-coded to reflect their abrasive levels, but pay attention because the colors are reversed here.
Yellow foam pads are more abrasive "cutting pads".
White foam is a fine finish pad.
Now you'll notice on the back of this white pad they put a color-coding chart on here. This is why I chose this photo. This is supposed to be the standard, but it's not always accurate.
The white and yellow foam pads are consistent in their cut ratings, but the other colors are not. It's always a good bet to check the packaging and talk to the sales rep when buying blue, green or black pads.
You see here that the black pad is rated for "heavy cut" from this manufacturer. I have 2 black pads in my shop that are softer than my white ones. See my point?
Cleaning foam pads is also different. Toss them in a sink of warm soapy water and massage them. Don't use hot water or get too violent with them...the velcro is attached to the foam with adhesive. They can be a bit fragile. Rinse them in cold water, squeeze out the excess and set them out to dry.
Instead of spurring them like your wool pads while you're buffing, use a damp terrycloth towel on the pad face while you spin it at 1800 rpm.