Generic mana is a cost that can be paid with any color, while colorless mana is a specific type of mana produced by certain lands and artifacts
Double Cross Double Deal Double Dip Double Header Double Play Double Take Drawn Together Duh Dumb Ass Elvish House Party Elvish Impersonators Emcee Enter the Dungeon Erase (Not the Urza's Legacy One) Eye to Eye Face to Face Farewell to Arms Fascist Art Director Fat Ass First Come, First Served Flaccify Flock of Rabid Sheep Forest
Lets take a look at Harsh Scrutiny in a different color combination: Creatures (5) Planeswalkers (9) Lands (26) Spells (21) Chandra, Torch of Defiance is the perfect card for a B/R Midrange deck, giving them another great two-for-one, a card draw engine, a victory condition, and extra mana to help make sure Goblin Dark-Dwellers comes on time
I was only ever happy to get my favorite Charmander buddy
Enchantments that tax the actions of the opponent's permanents Another offshoot of the last two categories is an enchantment (often an Aura but not always) that restricts the use of a permanent (most often a creature but not always) unless the opponent pays a tax (most often mana but not always)