So, we know that Akane is "light", but there was never any explanation of what that means in this elemental system. My half-guess is that, to contrast with "dark"s creation, it might be destruction, given that the largest things we've heard of or seen Akane doing involve wiping out large chunks of scenery.
It's probably important to remember, though, that these elemental types are tendencies and preferences rather than strict categories; all witches can presumably manipulate all the elements to some extent, it's just that some are easier than others, and there are limits to how deep you can go into suboptimal traits.