Right?! It's so cool! And it just totally confirms that Korrassami wasn't something they just threw in at the end to please the shippers, they've been planning and hinting at Korra being bi for seasons.

And, yup, that whole ep has the colour scheme too! I found these just from quick image search--
http://vignette2.wikia.nocookie.net/avatar/images/7/73/Unalaq_attempts_to_destroy_Korra's_spirit.png/revision/latest?cb=20131113015242
http://images.latintimes.com/sites/latintimes.com/files/styles/large/public/2013/12/05/1/60/16095.png?itok=YbTNyEir
http://fc01.deviantart.net/fs70/f/2013/319/8/7/_spoilers__korra_vs_unalaq_by_burnouts3s3-d6uem58.png
--which, yeah, I can't quite remember how her accessing that power went down either, but I'm pretty sure you're on the money that she'd lost the avatar state and was drawing on her own power.