I am looking for a product to cover the inside roof of the garage, it will be used to cover the insulation that is installed between the 2x6 in the roof, drywall is to heavy and I would like something that I can paint. Could I use 1" pink foam board and get paint to stick to it?

First make sure you have venting from the soffit to the roof vents between the insulation and roof. If not, your roof sheathing and shingles won't last but a few years with insulation up there and heat inside.

Don't forget to check the local building codes to see if what you decide on is legal. It would really suck to have to remove it later to sell the house.

I put White ribbed steel on my garage ceiling, because I wanted something lightweight enough to easily do myself. Comes in lots of colors, and will have way better durability than pink foam board. But to answer your question, yes paint will stick to that foam. There's also a greyboard that comes in 1" thickness that's pretty close to white in color.

Your homeowners insurance will take a dump on you if you have a fire and they find unprotected foam.

I used 7/16 OSB plywood for the ceiling and walls in my garage, I guess if I had it to do all over again I would have used Steel on the ceilings and still used the wood on the walls. The white steel reflects the light so well and is maintenace free. The other advantage to steel is the ease of installation, you can pretty much do the whole thing in a day with a little help from a sheet rock lift! It's a little more spendy but in the end I think you would be happy. (my 2 cents)