Looking at the rolls of 3M sandpaper for my sanding blocks and wondering what the difference is between the red, blue and gold rolls? These are the 3M stickit products and come in various grits. Should I use one for filler and in for primer final prep?

Is there something better for my sanding blocks? What seems to be the favorite?

The different color papers are just different qualities (good, better, best, wet, dry, paper weight, and so on). The grit determines what the paper is used for. Example: 80 grit is used to take a lot of material off fast but leaves deep scratches. 180 grit is used to refine what was previously done with the 80 and leaves smaller scratches.

Check out the "Info Center" link at the top of this page. It has a bunch of topics including: What Sanding Grit to use that will answer a lot of your questions.

Also, you may want to check out the "Paintucation Video - Body Shop Basics". It helped me a lot when I first started and was well worth the cost.

Hope this helps ~ Lenny B

Thanks Lenny. I understand grits and when they are used. If you look, 3M has their abrasives in categories: red abrasives, gold abrasives, purple abrasives, blue etc.

They all seem to have various grits available. From what I can tell there may be different weight paper backing?

Wondering which is the best or is it preference/cost?

3m hierarchy goes like this

Red
Blue
Gold
Purple
Dark purple

Big differences in price and quality. No one in my
area is using blue as far as I know. It's fairly new. I
think it's going to replace gold.

For the coarse grits I use Indasa or similar. If the grit varies in size it won't matter since you will be sanding with finer grits anyway.
For 220 - 400 I use 3M Gold. Norton is also good but pricing is very close to 3M.
Eagle Abrasives makes some pretty decent stuff as well. I bought a box of their 6" 80 grit discs and they last quite a bit longer than some of the other brands I have used.