🌼🌸 Let me assign a flower to your oc! 🌼🌸

I think Veronica would be really cute! They usually come in pink/purple too and they remind me of your character!

Hm. To be honest, I think Queen of the Night could work! This is due to they only open at night and it's a rare thing to happen if I recall correctly.  The opening up at night could be metophor for your character possibly opening to other characters or more. I think the lunar thing also reminded me of this flower.

For Emi, I think Sunflowers because of the eye color and they usually represent close bonds and positivity towards other people.
For Yuma, I went with Flowering bluets. This is due to Yuma's appearance. Blue and white hair, yellow eyes remind me of these flowers! 

This is gonna be weird take but trust me! Yellow Butterfly Bush due to the character's appearance which are yellow with little hints of red!

Since your character is a shy person, I thought the touch-me-not/shameplant would be cute! I thought this would represent their awkwardness and the flowers reminded me of Celeste!

Since your character likes primary colors (I forgot blue is a primary color but like DGFSYFDSG) I think Lantanas would be really cute! They're really colorful and tiny too like your character!