What does the Indigo layer of Prismatic Wall/Sphere do to buff spells?

Question

We encountered a creature which cast Prismatic Sphere/Wall and have been debating some aspects of the spell. In this case we are specifically talking about 6th layer, the indigo. What does it do to spells that are on someone but are not attack spells, like fly?

6th - Indigo

Stops all spells. Will save or become insane (as insanity spell).

So what does "Stops all spells" mean? The GM has read it as it ends other spells that come into contact with it. So if someone with fly were to touch that layer, fly is gone as if dispelled. I would personally read it as suppresses any spells (not on the caster) while inside the effect.

Answer 1

The designers admit the table's unclear

The first sentence in the spell prismatic wall's Effect of Color column occurs to effects from beyond the wall attempting to pass through the wall, while the second sentence in the Effect of Color column occurs to a creature itself when it attempts to pass through the wall. (The same applies to the spell prismatic sphere, too.)

Hence a creature with spells cast on it keeps those spells after penetrating the wall's sixth indigo layer much like, for example, the creature keeps its mundane ranged weapons after penetrating the first red layer and keeps its breath weapon after penetrating the wall's fourth green layer. The sixth, first, and fourth layers stop, respectively, spells, mundane ranged attacks, and breath weapons from beyond the wall from penetrating the wall; those layers don't also affect in those first sentences' ways a creature attempting to pass through the prismatic wall!

Pathfinder creative director James Jacobs in a 2010 Paizo messageboard post says

Objects, in this [prismatic wall] case, refers to nonmagical non-living things that are used to try to breach the wall. Like thrown rocks, thrown tables, arrows, catapult boulders, and so on. Any objects or items or whatever that are "attended" (as in, carried or worn by a creature) are NOT destroyed, but travel with the person carrying/holding them off to whatever other plane that person ends up going to. If the person makes their Will save to avoid being sent to another plane, he can stroll right on through the wall with all his stuff intact.

Allowing prismatic wall to automatically destroy every object that passes through it, in other words, IS a bit excessive. The intent of the spell is to prevent anyone from making ranged attacks with weapons or spells or abilities against those on he other side, basically, not to provide a static disintegration wall. The limitations of the table format forced us to be a bit more brief than we should have been in describing it, alas.

Artifacts can't be destroyed by a prismatic wall unless the Destruction line of the artifact says otherwise.

Thus the prismatic wall's layers have "their effects on creatures trying to attack you [with effects from beyond the prismatic wall] or [on creatures that] pass through the wall[, respectively]." However, this reader had to add all that bracketed information because, as Jacobs says, "The limitations of the table format forced us to be a bit more brief than we should have been in describing it, alas." (And that alas dates back to, like, at least the 2003 D&D 3.5e's description of the spell prismatic wall.)

For example, a typical creature that attempts to pass through the wall is dealt between 70 and 140 points of damage, and must make saving throws to avoid being poisoned, petrified, driven insane, and being sent to another plane, but the creature suffers none of the layers' other effects!

The creature, when passing through the wall, does not, for example, also see its mundane and magical ranged weapons destroyed by the red and orange layers, respectively, nor does the creature scratch its breath weapon off its character sheet because of the green layer, or see its spells dispelled by the indigo layer. Those layers simply stop those attack forms when launched from beyond the wall from reaching past the wall.

In other words, spells on the creature remain intact if the creature gets through the indigo layer of the prismatic wall, but spells from beyond the wall won't affect past the wall because the indigo layer stops all spells.

Answer 2

Prismatic Sphere references Prismatic Wall which says:

Each color in the wall has a special effect. The accompanying table shows the seven colors of the wall, the order in which they appear, their effects on creatures trying to attack you or pass through the wall, and the magic needed to negate each color.

So the indigo layer prevents all spells from passing through it. For a spell like Fireball or Magic Missile the effects are straightforward. For the situation you describe where a person under the effect of a Fly spell, I see 3 possibilities:

1. The spell cannot pass through and since the spell is tied to the person, they can't pass through either.
2. The person can pass through, the spell cannot so it is effectively dispelled.
3. There is no spell passing through, only a person under an effect of a spell that was never cast at or near the sphere - the person passes through and remains under the effect of the Fly.

None of these are prohibited by the wording so choose the one you like best and stick with it. Personally, I like No 3 since the overall thrust of the spell is to have different effects on creatures than on objects/effects.