When Nightmare Moon escapes after 1,000 years of imprisonment in the moon, only five teenagers with attitude can stop her; the Power Rangers Harmony Force.

Sunset Shimmer as the Red Ranger
Rainbow Dash as the Blue Ranger
Applejack as the Yellow Ranger
Rarity as the White Ranger
Pinkie Pie as the Pink Ranger (Obviously)
Later, Fluttershy as the Green Ranger
And also later, Twilight Sparkle as the Purple Ranger

Heavily inspired by 'Rainbow Sentai Harmonyranger' by Xero Key and Shadow-DJ
Links here: Rainbow Sentia Harmonyranger
Xero Key
Shadow DJ
Also inspired by both Power Rangers and MLP: FiM
Please note that I am in no way attempting plagiarism, even if some parts of story are very similar to what it was inspired by.
Disclaimer: I do not own either Power Rangers, MLP: FiM, or any of the characters in this story (except Press Pass and Spark Hedge).