I know I'm one of the like, 10 people in this fandom, but I was drawing her and wanted to analyze her name and color choice.
~Kinda long post~
Firstly, her name. The name Gemma has Latin and Italian roots and holds the meaning of precious stone. I at first didn't really have anything to connect this to, but I'll come back to it when I analyze the color of her outfit. Still, the name Gemma holds another meaning: Bud. I honestly like to use this interpretation just because of the flower she gave Kymara in episode 3 and the flower print on her undershirt. The idea of her being a bud that needs to bloom could relate to how global child sees her, and how she acts in the story. Global child needs kids because they are the next generation, they are the buds about to bloom. They want to control that. I also used this to bridge over to color.
Her last name, Khouri, has Latin and Arabic roots. The name means priest and is heavily related to Arabic Christians. Based on this, Gemma likely has some Middle Eastern descent.
While we learned where Gemma likely descended from, how do the name's meaning and color affect her character?
When in the base, gemma wears a green shirt over a green and blue floral patten button up shirt. She also wears tan khaki pants. The throughline of green relates to the idea of a bud, as buds are usually green. Green has always been closely related to nature, which pairs well with Gemma's character as she very much enjoys being outside and was raised on a farm.
When outside, Gemma wears an overcoat. I have difficulty discerning which color exactly her overcoat is, but it exists in the space from dark purple to burgundy. Both colors share a definition: sophistication. Weird, right? Being raised on a farm and running from an evil science group don't scream "sophistication", but this could be the point. Back to the other meanings of the name, Priests are religious leaders, they're the guiders of the group. This doesn't seem to fit Gemma as she isn't really the leader of the group, Rose is. Yet, when she goes out, she wears that overcoat like a mask. The coat is dark and blends in, like she needs to in the scenes she wears it in. She has to seem like she's supposed to be there or else she'll be in danger.
Gemma's name means precious stone. In the narrative, she is. About 3/4 into the story, she is one of the few unlisted kids not caught, she's an oddity. This also reflects with her hat. It's bright red. It's one piece that sticks out in her outfit, and is what raises the suspicion of global child when they come to the twins' house. Unlike Kymara, Gemma is good at acting the way she needs to go outside, but she isn't fully invisible. Her red and purple outside add-ons contrast with her mostly green base clothes, going back to the mask she wears.
If you really want to stretch, Gemma's golden yellow glasses, which hold ideas of enlightenment, could connect to her priestly surname, who are enlightened people. She acts as support for the group and is often the first to question a decision because of fear.
I know that the reason she and the other unlisted kids wear the clothes they do is because those were the clothes they found on the street, but it's fun to analyze names and colors.
Anyways, I think Gemma's favorite color is either yellow because of her glasses, or green because of the farm. (❁´◡`❁)