How does crew power affect ships?

They look like these. They can only be placed on characters at G12 minimum, are upgraded from 5 dot mods.

The more you upgrade them the stronger the mod, keeping in mind upgrading mods with no speed isn’t going to do you any good.

6E is white, 6D is green, 6C is blue, 6B is purple, and 6A is gold. The materials to upgrade a mod through these tiers aren’t the easiest to acquire early game.