Most spells come in one of five colors. To play a spell of a given color, at least one mana of that color is required. This mana is normally generated by a basic land: plains for white, island for blue, swamp for black, mountain for red, and forest for green. The balances and distinctions among the five colors form one of the defining aspects of the game. Each color has strengths and weaknesses based on the "style" of magic it represents.
White is the color of order, equality, righteousness, healing, law, community, peace, absolutism/totalitarianism, and light. White's strengths are a roster of small creatures that are strong collectively; protecting those creatures with enchantments; gaining life; preventing damage to creatures or players; imposing restrictions on players; reducing the capabilities of opposing creatures, and powerful spells that "equalize" the playing field by destroying all cards of a given type. White's weaknesses include a focus on creatures, its unwillingness to simply kill creatures outright, and the fact that many of its most powerful spells affect all players equally—including the casting player.
Blue is the color of intellect, reason, illusion, logic, knowledge, manipulation, and trickery, as well as the classical elements of air and water. Blue's cards are best at letting a player draw additional cards; permanently taking control of an opponent's cards; returning cards to their owner's hand; making cards go directly from a player's deck to their graveyard; and countering spells, causing them to be discarded and the mana used to pay them wasted. Blue's weaknesses include having trouble permanently dealing with spells that have already been played, the reactive nature of most of its spells, and a small (and expensive) roster of creatures.
Black is the color of power, ambition, greed, death, illness, corruption, selfishness, amorality, and sacrifice; it is not necessarily evil, though many of its cards refer directly or indirectly to this concept. Black cards are best at destroying creatures, forcing players to discard cards from their hand, making players lose life, and returning creatures from the players' graveyards. Black's main weaknesses are an almost complete inability to deal with enchantments and artifacts, its tendency to hurt itself almost as badly as it hurts the opponent, and difficulties in removing other Black creatures.
Red is the color of freedom, chaos, passion, creativity, impulse, fury, warfare, lightning, the classical element of fire, and the non-living geological aspects of the classical element earth. Red's strengths include destroying opposing lands and artifacts, sacrificing permanent resources for temporary but great power, and playing spells that deal "direct damage" to creatures or players, usually via applications of fire. Red's weaknesses include its inability to destroy enchantments, the self-destructive nature of many of its spells, and the way in which it trades early-game speed at the cost of late-game staying power. Red also has the vast majority of cards that involve random chance.
Green is the color of life, nature, reality, evolution/adaptability, ecology, interdependence, instinct, and indulgence. Green's strengths are on the battlefield, usually winning through combat with creatures, of which it has a broad menagerie. These tend to be strong for their cost and have abilities that make them more survivable. Many Green spells bolster its creatures' power, either permanently or temporarily. Green spells often focus on growth, such as regaining life points and getting lands faster, thus allowing the player more resources and the capacity to get strong creatures on the battlefield faster. Green's weakness is an inability to defend against indirect attacks.
The colors adjacent to each other on the pentagon are "allied" and often have similar, complementary abilities. For example, Blue has a relatively large number of flying creatures, as do White and Black, which are next to it. The two non-adjacent colors to a particular color are "enemy" colors, and are thematically opposed. For instance, Red tends to be very aggressive, while White and Blue are often more defensive in nature. The Research and Development (R&D) team at Wizards of the Coast aims to balance power and abilities among the five colors by using the "Color Pie" to differentiate the strengths and weaknesses of each. This guideline lays out the capabilities, themes, and mechanics of each color and allows for every color to have its own distinct attributes and gameplay. The Color Pie is used to ensure new cards are thematically in the correct color and do not infringe on the territory of other colors.
^"Card of the Day — July, 2006". Wizards of the Coast. July 27, 2006. Retrieved September 30, 2006. Black removal spells like Terror or Dark Banishing that could take out large-sized creatures historically had the drawback of not being able to affect other black creatures, and sometimes not artifact creatures either. Since then this drawback has been tweaked in many ways that no longer limit the cards to just non-black or non-artifact.
^Brady Dommermuth (February 1, 2006). "Ask Wizards". Wizards of the Coast. Retrieved September 26, 2006. The particular issue of red's connection to earth and stone has another aspect as well, though. Red has and will continue to have earth/stone-themed cards. But green wants to be connected to earth as well, in the soil sense. So red gives up a few of its 'earth' cards for green's sake.