Bound In Blue: Book One Of The Sword Of Elements

When Rhi discovers that beings out of myth and legend are real, her ability to see magic as color puts her at the center of a conflict with the ancient gods of Avalon. She must somehow master her power and use it to remake the Sword of Elements - once known as Excalibur - but if she succeeds, she could become far more dangerous than any god.

And gods don't like being challenged.