Mark Rosewater explains the new colorless mana symbol in detail in "A Solemn Oath, Part 1." So, when deck building, you will want to make sure to support any colorless cards you play
Whenever another creature leaves the battlefield, Flaming Fist Officer will get a +1/+1 counter
This deck would cast Squandered Resources, sacrifice all lands to Natural Balance, then cast Cadaverous Bloom, and then pitch cards to generate mana and draw more cards
But figuring out why an Earth Elemental could kill an Air Elemental and survive was different from math homework, it was fun
Your best bet against aggro is going to be using Madam Mim an Snake to bounce and attack and clear your opponents board
Belle in particular looks great as a playable card in an already-popular ink combo