on my 87 caddilac i have a whit vinyle top..it has some greyish discolor to it and some wear.
my question is can it be painted and if so what would be the best paint to use?

 

Yes, it can be painted, but I don't recommend it. After a short time it starts to crack and its worse than the original problem. The paint fills in the texture and you have to be very careful washing it so it doesn't come off, regardless of what the manufactuer says. Looks like someone tried to dress it up on the cheap side, kinda like Wal-Mart spinners. Even though it can be expensive, better off replacing it.
Unless you want your car to look original, maybe consider a carraige roof? They are very classy.