For a party of three what is your recommendations for classes.
Please explain why and please give a little more specifics on the class (ex. Abjuration wizard, Darkness cleric etc.)
When I did Crimson with a 4 person party, it was with a Bard X / Paladin 3, an Arcane Trickster (don't know specific breakdown), an Arcane Sorcerer, and a caster Cleric (guessing he was healer build of some sort).
The Cleric felt like a must have for some of the events, and with any campaign you want decent amounts of Dispel Magic at high levels. A solid Diplomacy got us past a lot, and having only one excellent melee character worked out okay (although the Trickster joined in the melee once he realized bard buffs actually let him contribute that way).
So a three person party I'd probably suggest something like Paladin, melee Cleric, general purpose Wizard. Give or take, there's other classes that can work in some of those rolls.