Prism color and their buff values:
Red - Enthusiasm 10BG/T (Basically Zeal w/o DoT)
Orange - 50% Crit dmg, ??% Proc rate but pretty damn high in my experience
Yellow - 35%? Light dmg (Mike AW's buff misses but Durga's overwrites it, so >30% and <40%)
Green - 40% Vigor
Cyan - 50% DA
Blue - 50% TA
Purple - 10% Special Attack
Rainbow - ALL of the above
Bit of my two cent, I have never had an instance where Iris's RNG was bad. The bottom line is, none of her 7 buffs is bad. Even the seemingly 'weakest' one is a whopping 50% DA, and it's extremely rare that you get only one color several times in a row as their chances are pretty even.
It was 11m.
That being said, it wasn't even the highest since my single target record is 5m, off element.
And no I didnt say Light is required to get Medea. I said Medea is top pick if you are competitive in Tower and Dummy regardless of element. For raids, while Medea is also relevant since her utility is also quite broken, Hektor is the top MVP stealer right now against weakness, and is the only one I seen that can steal against Shingen in an even fight.