"A little idea I came up with not to long ago.

The idea is that when you look at Celestia and Luna's manes, they're see through. You can still touch them (and they're very soft, like silk), but when you look through them, you can see what that particular are would like like during night or day. If you look at a patch of sunlight through Luna's mane, you see night. If you look at a patch of moonlight through Celestia's mane, you see day.

Their manes are still able to be styled and what not, but I thought this was a cool idea. The only part that isn't see through would be the parts covering their horns, like on Luna's head."