These designs are cool. Each character has its own appeal with its own trait.
The left one, the teeth, the eyelashes, and the hair—those are the appeal. They shine in the emo style; most emo use black hair. And you use blonde hair and bright color. That's powerful and so impactful.
The center one is the strongest one for me. It's innocent, it's simple, but it's catchy in the eyes. Orange in the dark color is so bright. The appeal of this one is the mix of these colors. The orange is really showing the real trait of the character. It can be greater if the hair and the shoes have distinct colors. The hair you can add a little black or a little bit of red. The shoes, you can use a color opposite of orange.
Try to avoid the same color as you have a solid color style. If you use the same color or the same style, it makes your design not powerful enough.
Last one, the right one, for me, is the weakest among the three. You mix a lot, and the appeal is not showing in my eyes.
You use short pants, but the clothes are so formal. From the eyes, I feel this character is so carefree, as you add two lines below the eyes. It indicates chill and carefree with the mouth too.
The top is good, yet the bot is like a different character. Using black distracts and derails the top of the character. You have a bright, goofy, and carefree design, with the hair color and the clothes. Yet suddenly, you use black short pants and black heels.
In my view, you need to maintain the image of the top of this character, because it's amazing. You can use the color of the clothes for your short pants and the shoes, or the color of your hair. The tie just keep it black.
*Additional
You can maintain the pants black, yet the shoes need to change the color
It's like a border. The carefree persona on top, and the shorts as a border or a break.
Each character has own appeal. That's amazing.