No, you cant use colorless mana for any color, as colorless mana can only pay for generic costs or specific colorless requirements
When crafting cards to build decks youll want to make sure that youre going to get a lot of mileage out of your Rare and Mythic cards if youre using them for Standard
You can point this at opponents to finish them off, which is awesome
Keskit, the Flesh Sculptor + Armix, Filigree Thrasher Im honestly surprised that so few know about the one-two punch that is Keskit, the Flesh Sculptor and Armix, Filigree Thrasher
This fits right into the Miracle Worker deck, but that deck was all about the miracle mechanic and setting up your library to be able to draw them and get that sweet sweet discount
If you're hoping to open something iconic, but don't want to play a colorless-themed deck with Ugin, perhaps I can interest you in the other card pre-selling for $80: Mox Jasper