When running through the possible test subjects that would appreciate an invention like this, one name immediately sprung to his mind. Tammy.
If he thought his issues with bullying were bad, that all went double for poor little Tammy. Standing at an adorable 4'10" at 16 years old, she would be pushed around like nobody's business. "Runt", "Gremlin", "Doorstop", she's heard them all before. Justin's heard her crying in the bathroom at least twice.
Because of this, Justin was one of the few people she could actually trust and get along with. When she was at home, she found her escapism through video games. RPGs, especially.
After a quick phone call and bike ride, Justin made his way to Tammy's place. He knocked on the front door and was greeted by Tammy's mother.
"Oh hey, Justin. Tammy told me you were coming. She's in her room." She explained.
"Thanks, Mrs. Tesmer." He replied.
"I'm have to be at a dentist appointment, and her father's out with his friends, so I'm trusting you two to be home alone. Don't do anything you know you're not supposed to."
"Oh my god!" Justin jokingly exclaimed.
Justin walked down the hall, knocked on Tammy's bedroom door and let himself in. Tammy was sat at her computer playing The Elder Scrolls: Online.
"Did I catch ya while you were doing something?" Justin asked.
"Oh, uh, no. This actually a good stopping point. So what's all this about?" Tammy responded.
Justin paused for a moment, and before answering the question asked, "I thought you said that game sucked ass?"
"It got better after the DLCs. But no, seriously, why did you want to come over?"
Justin paused for dramatic effect and sat his backpack down on the floor. "I... have a surprise for you." He paused again... "What if I told you, that in my chem lab, I made a serum that can make you bigger and stronger."
Tammy, in a very poor attempt at doing a low-pitched grungy voice, said, "Don't do that. Don't give me hope."
"No, seriously, it's for real!" Justin shot back. "Remember that award I got a few months back, that was because I got the serum to work on live rats!" It was at this point that Justin pulled the 3 vials out of his backpack and sat them on Tammy's desk.
"So now..." Tammy continued, "You want me to try it."
"Well... honestly, I was all prepared to try it myself right out the gate, but for god knows what reason, it works less than half as well on men... and, more importantly, you kinda needed it more than I did. I've been bullied, but you've been massacred! I figured you would appreciate first dibs."
"That, and you need to make sure it doesn't give you super cancer?" She smirked. Justin nervously pulled his lips in before Tammy continued. "I'm just messing with ya. I actually do really appreciate this. So how does this work?"
"Blue is for light growth, Yellow is for moderate, Red is for extreme. Do whichever you're comfortable with."