The Hidden Forest

Does prismatic focus cover all 5 resists or just cold, fire and ,magic?

I don't know of any Prismatic foci on the server, but there are Chromatic foci.

Prismatic do a resist check against the average of the boss's resists (fire/cold/poison/disease/magic).

Chromatic do a resist check against the lowest of the boss's resists.

Chromatic sorry, any if I purchased the chromatic arc5 focus aug which spell types get the benifet

buff procs mostly, spirit of the lion, mana flare, etc.

If you look up the spell on the Alla Clone here, you'll see the resist type. Chromatic Arc I-VII will affect any chromatic resist type spell.

Example: webtools/spell.php?id=8685

As Warl mentioned, it's mostly shaman proc buffs and enchanter spell proc buffs.