Here is a helpful list of different Lanterns' Crops.

The Green Lantern Corps
Color: Green
Emotion: Willpower
Entity/God/Power Source: Ion
Prime Lantern/Leader: Applejack
Oath:
In brightest day, in blackest night
No evil shall escape my sight
Let those who worship evil's might
Beware my power—Green Lantern's light!

The Sinestro Corps
Color: Yellow
Emotion: Fear
Entity/God/Power Source: Parallax
Prime Lantern/Leader: Twilight Sparkle
Oath:
In blackest day, in brightest night,
Beware your fears made into light
Let those who try to stop what's right
Burn like his power —my yellow might!

The Blue Lantern Corps
Color: Blue
Emotion: Hope
Entity/God/Power Source: Adara
Prime Lantern/Leader: Pinkie Pie
Oath:
In fearful day, in raging night,
With strong hearts full our souls ignite,
When all seems lost in the War of Light,
Look to the stars—for hope burns bright!

The Red Lantern Corps
Color: Red
Emotion: Rage
Entity/God/Power Source: Butcher
Prime Lantern/Leader: Rainbow Dash
Oath:
With blood and rage of crimson red
Ripped from a corpse so freshly dead
Together with our hellish hate
We'll burn you all— that is your fate!

The Star Sapphire Corps
Color: Violet
Emotion: Love
Entity/God/Power Source: Predator
Prime Lantern/Leader: Fluttershy
Oath:
For hearts long lost and full of fright,
For those alone in blackest night,
Accept our ring and join our fight,
Love Conquers All— with violet light!

The Orange Lantern Corps
Color: Orange
Emotion: Avarice
Entity/God/Power Source: Ophidian
Prime Lantern/Leader: Applebloom/Spike
Oath:
What's mine is mine
and mine and mine.
And mine and mine and mine!
NOT YOURS!

The Indigo Tribe
Color: Indigo
Emotion: Compassion
Entity/God/Power Source: Proselyte
Prime Lantern/Leader: Rarity Belle
Oath:
Tor lorek san bor nakka mur.
Natromo faan tornek wot ur.
Ter Lantern ker lo Abin Sur
Taan lek lek nok-- formorrow Sur!

Black Lantern Corps
Color: Black
Emotion: None (Death)
Entity/God/Power Source: Nekron
Prime Lantern/Leader: Commander Hurricane
Oath:
The blackest night falls from the skies,
The darkness grows, as all light dies,
We crave your hearts and your demise,
By my black hand— the dead shall rise!

This will be updated when/if there is additional things to add.

2461350
Entity? Which entity? theres a lot of them about.

2461359

Main/God/Source of their powers

2461383
Ah. thanks.

Prime Lanterns

Green: Applejack

Yellow: Twilight Sparkle

Red: Rainbow Dash

Indigo: Rarity Belle

Violet: Fluttershy

Black: Commander Hurricane

Blue: Pinkie Pie

Orange: Applebloom

Spike, "No! The light is mine!"

Applebloom, "MINE!"

Spike, "MINE!"

2462542 I wonder how pleased the Orange Light will be to have two wielders fighting over it?

2461350
Shouldn't Cadance be leader of the Star Sapphires?

Ya know, cuz she's the princess of LOVE?

3135778

The First Star Sapphire Ring in Equestria went to Fluttershy so that means she's the leader of the Star Sapphires.

3135834
Still is garbage that she is the leader. Cadance should've been the leader, not Timidshy who belongs in the Indigo Tribe more than the Star Sapphires.

3135840 Actually The Indigo Tribe only takes.... criminals. Tell me does Fluttershy look like a criminal?

3136061
The Indigo Tribe is Compassion and Fluttershy has more of that than anypony else on the show, especially Rarity who gets into fights with the other Mane 6.

3136085 Yes but it's the only good parastie Corps. You go with them but once you leave it you totally forget everything you did while you were a part of it. It's more of a redemption Corps.

3136090
So put her in the Blue Lanterns with Pinkie or something. She is NOT leader material for the Star Sapphires at all.

3136097 She loves her animals almost like her family. She loves everypony this way and therefore she wouldn't be a hope bringer or a compassionate redeemer.

3136108
She isn't leader material, though. She's a peon if anything, like Fatality. Cadance, since her special talent is love and she's a princess, is more of the leader type like Wonder Woman.

3136151 Well Fluttershy would overload the Indigo Tribe due to her being over-compassionate.

Just to put an end to this. Fluttershy has the compactly to be either a Star Sapphire or a member of the Indigo Tribe. While the tribe's members are all sociopathic serial killers, there are exceptions to this rule.

1. During the Blackest Night event, the Atom was chosen/deputized to wield the indigo ring because he felt true compassion.

2. Kyle Rayner, learned how to control the indigo light during his journey to master the Emotional Spectrum.

So in conclusion, Fluttershy can be an indigo tribesmen or a star sapphire. Honestly it's up to whoever, many of the Mane 6 show attributes that can align to any of the 7 lights, just depends on your perspective.