Vinyl Headliners stains

If replaced make sure they use monel staples. You may want to look on the net for an upholstery forum. There's one in particular that has a few members that do bimini's and boat cushions. I can't recall the name offhand

If it's spots, it generally is mold that is on the back side of the material and coming through the front of it. Which will show as grey or even a red wine color a lot of times. Staples will generally show as a rust color. If you can get to the back side, spray it with a marine fabric mildew remover. I would highly recommend using a de-humidifier to get your humidity down. Getting your humidity way down may cause them to go away on their own.

My first thought was mold or mildew as well. Most modern air conditioning controls have a dehumidifier setting. Use it always when off the boat.

Auto body and paint supply shops sell vinyl dye in spray bomb cans. They cover very well and look good as well. You would have to remove the panels and do them all. But it's cheaper and easier than replacing the vinyl.

If the spots are from mold on the backside of the material they will come through the vinyl dye as well. I also don't recommend using the vinyl dye if your vinyl is in good condition otherwise because it changes the texture of the vinyl (makes it stiff) and also will eventually peel off.

While I agree if your vinyl is in good condition otherwise and you can get it clean and remove the spots I wouldn't bother dying it. But for what it's worth, I've done a number of exterior cushion sets with spray vinyl die and I've never had it peel, never had it stiffen the vinyl that I noticed and spots and stains did not bleed through. The dye, at least not the ones I've use, is not like a paint that sits on the surface of the vinyl, it seems to soak in like the name dye would imply. I used the Dupli-Color and SEM brands as I recall. And since they are designed to be sprayed on very flexible surfaces like shifter boots, they don't crack or peel.

But as they say, YMMV