Miriam and Aaron both complained about Moses' Cushite wife in Numbers 12:1. Why was only Miriam punished? Perhaps Miriam is mentioned first because she instigated the complaint against Moses? Miriam means bitterness. Aaron means light-bringer. Was there a difference in their motivations and attitudes?
What exactly was Miriam's complaint? Was she complaining on behalf of his wife or because of her? Maybe Miriam complained that Moses married a Cushite instead of an Israelite. This might be reflected in her punishment: turning completely white.
Regardless of ancestry, we are one nation in #messiah, adopted into the Commonwealth of Israel. The color of your skin, the flags and faiths of your parents, etc., are irrelevant to your salvation. Your obedience and the state of your heart matters.