When designing a character it's important the clothing and color palette fit the theme of the story. For example it wouldn't make sense for Amiree to wear clothing that's fully covers up her body. Since Amiree was a prostitute (someone who has sex for money) she would have to wear revealing clothing instead. For color palette observe the characters and setting. For example if your oc belongs to an dystopian world (A world wear great suffering and injustice is present) having them wear bright colorful wouldn't make sense since the theme is dark. Another example is when i was designing my danganronpa oc, haruka, she was originally supposed to be in the first game, but since she had bright colors i decided that she would we better in the second game since brighter colors are more present.