Iaya, Who Holds Color

Whenever you draw a card for the first time each
turn, you may look at the top five cards of your library. You may reveal a multicolored card from
among them and put it into your hand. Put the
rest on the bottom of your library in any order.
For each color, if a card of that color has been revealed from your library this turn, spells you
cast cost one less mana of that color to cast.
"Mana defines all."