Physical space is also a concern and is an issue that crops up in decks with three or more colors
(If this is in your deck, please keep track of your turns

Antiquities Square Cut (Misprinted Back) 1994 - Metal Cards, Press Checks and Production Anomalies Champions of Kamigawa Textless Cards - Metal Cards, Press Checks and Production Anomalies Fallen Empires (Wyvern Back) 1994 - Metal Cards, Press Checks and Production Anomalies Green Scrap Sheet (MTG Back) - Metal Cards, Press Checks and Production Anomalies Metal Cards - Metal Cards, Press Checks and Production Anomalies Mirage Japanese (Amstel Beer Back) - Metal Cards, Press Checks and Production Anomalies Nemesis Textless Cards - Metal Cards, Press Checks and Production Anomalies Number Cards (From Fifth Edition Simpliflied Chinese Boosters) 1998 - Metal Cards, Press Checks and Production Anomalies Pokemon German Cards Square Cut (MTG Back) 1999 - Metal Cards, Press Checks and Production Anomalies Scourge Theme Decks (Harry Potter Back) 2003 - Metal Cards, Press Checks and Production Anomalies Unlimited (Unlimited - Antiquities back) With Round Corners 1993-1994 - Metal Cards, Press Checks and Production Anomalies Urza's Destiny Textless Common Cards (Round Corners) 1999 - Metal Cards, Press Checks and Production Anomalies Urza's Destiny Textless Uncommon Cards (Round Corners) 1999 - Metal Cards, Press Checks and Production Anomalies Urza's Destiny Textless Rare Cards (Round Corners) 1999 - Metal Cards, Press Checks and Production Anomalies Urza's Destiny Textless Promos 1999 - Metal Cards, Press Checks and Production Anomalies Urza's Saga / Fourth Edition Textless Promos 1999 - Metal Cards, Press Checks and Production Anomalies

Are you buying a Double Masters box
Best Red Card: Etali, Primal Conqueror Etali, Primal Conqueror is technically a Gruul creature with green identity, too, but considering that you need red mana to cast it face up, I am listing it as my favourite red card
Really, if you have so much mana to spend at the end of the game, anything else would be better