Okay... I am not familiar with this anime, and I don't fully understand the information I've pieced together from TVTropes and snippets of Youtube vids.
But I believe this to be My-Otome (Wikipedia, TVTropes). In particular, I think this is its prequel series, My-Otome 0~S.ifr~.
I remember the girls going to an all-girl school together.
The main characters all go to the "Garderobe Academy". I THINK it's an all-girls boarding school intended to train the Otomes.
Each girl gets an earring to "seal" the pact with whoever to use the power.
They certainly all use earrings to morph into their superhero forms. Here's a couple of Youtube screenshots of the earrings:
eyes say something like "blu rose lvl restriction lifted".
Here's a screenshot from when one character used the blue earring:
That "end restriction" may not be part of the usual morph sequence for that earring. But the below text is:
Each color (blue, black, red, green) is different with different powers.
...
The black power is "evil" and I remember the girl getting it by bonding(?) with some young boy who is a typical a**hole.
This is supposedly the "Ultimate Black Diamond" that Nina uses in the main series, although despite the text it doesn't look black:
As for it being evil, the series wiki states:
Nina carries the Ultimate Black Diamond ... and forms a contract with Nagi. It's later revealed that the Ultimate Black Diamond is the corrupted Pure White Diamond.
And TVTropes states:
Her Ultimate Black Diamond, according to the character guide, is representative of her "extreme and mostly selfish" love for Sergay, which is antithetical to the Otomes' selfless devotion to their masters.
I think she gets an emerald to use instead in the sequel series, My-Otome Zwei.
As far as I can tell, this person, Nagi Dài Artai, is the "boy who is a typical a**hole".
When it's time to fight they "ask" something/-one for permission(?) to activate their power.
TVTropes states that "the Otomes' powers can only be activated by the vocal command of their 'masters'."
That said, there may be at least one situation where an Otome activated her power without permission. This video is from the third episode of the prequel series. In it, Lena/Rena has entered an even more powerful version of her morphed form, known as "Super Meister". In this form, the glowing bands that suppress the Otome's power and keep them bound to their "masters" have shattered. We see the broken remains of those bands falling away from her costume in this screenshot:
(This is also a different version of her usual superhero costume. It's not just the bands vanishing.)
This video gives us more context. I think she enters the unrestricted morph form to protect her daughter. Here is a close-up screenshot of the text on her earring as she morphs:
