Hey, so i've been wanting to do a 100% free to play visual novel, but i can't draw the characters myself

I though about ai, but the downside is that when i generate different facial expressions, the overall colors slightly changes, which would ruin the vn when people will be playing (i xan still do backgrounds tho)

But i can't afford to pay an artist (+ i'm minor so i don't have any credit card), so how could i do ? Free artists?

It's just needed to do the different characters emotions, i can still generate one ai art and then Ask the artist to change the face with different emotions, but do people do that?

Should be possible for an artist to change expressions of a character you made from AI. However, it's not guaranteed that they'll do it for free. There's some artists out there that provide free art, if you look hard enough you might find some but I'm not familiar with VN assets. 

You can try reaching out to different groups and social media sites like reddit  or gamedev discord groups, and honestly tell them that you cant afford artists and ask them if anyone can provide some free assets. I'd imagine some would be happy to provide as long as you credit them or they get something out of it aside from money.