It's a colloid. You're right that colloids vary; they can come in either forms of liquid, solid, or gas. However, colloid is the SPECIFIC answer. You can break everything down in those three states of matter, but pudding is a mixture, which makes it a colloid, but since it takes on the shape of its container (while maintaining its volume) it's in a liquid form. It is both a liquid and a colloid, but stating that it's a colloid is more specific.

Milk is a colloid, for example, but you would classify that as a liquid also.

EDIT: I guess to be correct then, yes b00bles wasn't entirely right when she stated that it wasn't a liquid, because colloids (by nature) come in the various states of matter.

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all i know is that mixing pudding with some medicines, it turns into a liquid.

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Pudding may be a colloid, but that wasn't the question. The question referred to the specific phase of matter for pudding. Colloid describes a chemical state, not a phase of matter.

The answer is that the phase of the pudding is entirely dependant upon it's composition. Some puddings may qualify as solids, and some as liquids, mostly dependant on their water content. Some may start as liquids and become solids as they dehydrate through evaporation or sublimation. A pudding with less water content will tend to resist deformation and changes in volume. A pudding with too great a water content will tend to free-flow and may assume the shape of its container or be constrained by solids, and thus qualify as a liquid.

It's definately not a plasma as plasma refers to a distinct form of ionized gas. Plasmas also usually exhibit temperatures >1000 C... which would definately ruin most civilian pudding brands.

So, long and short answer: properly prepared pudding = solid as it lacks the internal fluidity required to be classified as a liquid.

Im not a scientist but I think its a liquid with some substances that are solid (powder with water or something....)
I say its a liquid.