I have a background in mold and work in a related industry. Here are a couple points to ponder:
-In addition to water, mold requires a food source which must be organic. Your foam insulation is likely a polyurethane foam and, although organic (contains carbon and hydrogen), it doesn't support mold growth. It is likely dust and other accumulated debris on the foam that is supporting the mold growth.
-The color of mold is not an indicator of it's genus/species. Just because it is "black mold" doesn't mean it is Stachybotrys. But that doesn't mean you want to live with it.
-On an open cell foam product, mold you can see is just on the surface. It has extended "roots" (hyphae) down into the foam. So, surface sanitizing won't kill it all.
-I would seriously consider a way to remove and replace the foam (e.g., Great Stuff, or if it may be exposed to heat, a fire-rated foam). As a last resort, if you can't remove the foam and you're confident it will not continue to be exposed to humid/moist conditions, you can sanitize it (bleach), let it dry thoroughly, and encapsulate the foam/mold with a product such as Kilz (spray paint). This will prevent future mold growth if it is kept dry and prevent the mold inside the foam from contaminating the surrounding environment.