The Color of Their Mana

Well, this gets rid of the Fluttercry. From my own comment section for Twilight Sparkle, Planeswalker:

[Semi-canon commentary on own story. Not set in stone.]
On talks of mana alignments:
I consider Equestria to be a white society. Different locations within the settled parts of Equestria favor different parts of the color wheel, but the ideological components (both positive and negative) of white is what most ponies are taught while they're being socialized. So having white impulses doesn't mean they're white so much as that's what's expected of them.

The Mane Six tends towards mono colors right now:
Twilight: Blue- logic, intellect, omniscience (she wants to know it all)
Applejack: White- uncreative, moral, law
Pinkie Pie: Red- chaos, action, short sighted
Fluttershy: Green- interdependence, nature, naive
Rainbow Dash: Red- impulse, freedom, action
Rarity: Black- selfish, omnipotent, paranoia (small amounts unless she's acted upon by an outside force)

For Rarity, black seemed like the most appropriate color. Each color can have positive and negative moral implications. For Rarity's case, she is selfish and ambitious, but that's directed towards her work. She doesn't cut other people down or suck out the benefits of the system, she makes beautiful clothes and is generous with her gifts. It's all an exercise in enlightened self interest, and as a social rouge she's rocking it pretty well.

I realize this sort of thing leads to a lot of debates, but there's a SpaceBattles thread for this story. I might also make a blog post so that people can go at it without cluttering up the comment section with debate.

Comments

[FanOfMostEverything]

Let the nerd arguments begin!

Twilight: Blue, without a shadow of a doubt. Analytical, logical, thoughtful, and seeks nothing more than she does additional knowledge.
Applejack: Green. Simple, traditional, practical, less interested in changing the world than working with it the way it is. Puts more trust in gut and hooves than in brain.
Pinkie Pie: Red/black/white. Hedonistic, manic, unpredictable, unrestrained, scoffs in the face of laws of pony, nature, and physics. Motivated almost exclusively by own desires (which, thankfully, largely entail parties.) Definite capacity for actual insanity. Friends and adopted family are precious and beloved. Everypony else? Prank fodder. Just enough white to make her wacky rather than sociopathic.
Fluttershy: Green/white. Gentle, loving, nurturing, resolute, friend to all living things. Pray if you harm those under her aegis, for nothing else shall save you.
Rainbow Dash: Red/white. Loyal, devoted, proud, aggressive, driven, direct, smarter than she thinks, softer than she seems.
Rarity: White/black. Overbearing, demanding, controlling, ambitious, thoughtful, sophisticted, willingness to sacrifice self and others, loving towards an "inner circle" while aloof towards those outside it, split between charitable and selfish desires.

[Kiue Jin]

Now that you mention it, Rarity is a rather good candidate for White/Black, due to her mixture of Selfishness and Generosity.

[Aranfan]

If anything I'd say Rainbow Dash is Red/Black. The loyalty isn't really the white kind of loyalty based on duty, it's based on "these are my friends and if you hurt them I hurt you" which is red. And Dash is certainly arrogant, egotistical, and ambitous enough for black.

[Alaborn]

Based on their observed characteristics, I'd go with the following.
Twilight Sparkle: Blue or Blue/Red
Applejack and Fluttershy: Green and/or White
Pinkie Pie: Red
Rainbow Dash: White and/or Red and/or Black
Rarity: White and/or Black

As Magic cards for a hypothetical expansion set on Equestria, with a desire to make these creatures monocolored and split among all five colors, I came up with the following. (Keywords for the set are Friendship, sharing X damage in combat, and Magic, searching the top 5 cards of the library for a instant, sorcery, or enchantment with CMC X.)

Fluttershy – 2WW
Legendary Creature – Pegasus Druid
Flying, Friendship 2
When a creature with one creature type enters the battlefield, you may pay 1. If you do, draw a card.
3/3

Rarity – 2WW
Legendary Creature – Unicorn Citizen
Friendship 2, Magic 3
When Rarity enters the battlefield, you may search your library for an Aura or Equipment card, reveal it, put it into your hand, then shuffle your library.
Rarity gets +1/+1 for each Aura or Equipment attached to it.
3/3

Twilight Sparkle – 2UU
Legendary Creature – Unicorn Wizard
Friendship 2, Magic 10
Whenever you cast an instant or sorcery spell, if it does not share a name with an instant or sorcery spell in your graveyard, you may draw a card.
3/3

Rainbow Dash – 2BB
Legendary Creature – Pegasus Scout
Flying, Haste, Friendship 2
Rainbow Dash deals combat damage at the end of the declare blockers step, not during any combat damage step.
“I ALWAYS win.”
3/3

Pinkie Pie – 2RR
Legendary Creature – Horse Citizen
Friendship 4
Prevent half the damage that would be dealt to Pinkie Pie, rounded down.
When Pinkie Pie becomes the target of a spell or ability, you may exile Pinkie Pie, then return it to the battlefield.
R: Pinkie Pie gains flying until end of turn.
3/3

Applejack - 2GG
Legendary Creature – Horse Citizen
Vigilance, Friendship 2
T: Add GGG to your mana pool.
3/3