Why is the castle emanating this glowing purple light? There is also some around it in the weird dark haze.

 

Edited June 8, 201610 yr by Keyblade master26

Either it has something to do with the story, or it is lighting and made to be there to make the place seem alive. I sort of remember this from BBS, since there was some lighting in the almost same spots as this to make it feel like an actual place. I don't understand how there is electricity at all in the dark realm, however. So maybe that could use some explaining, but I think it is just to so that the place is active and not just dark and broken looking.

most likely just to give it a more ominous look to it

Either dramatic effect, or dark energy. 

Cinerella is set in a time when they would've had gaslamps, so there's no way it's regular lighting. 

I'd go with "Purple is spoopy" as the reason. It's just for effect. 

It's the Realm of Darkness afterall.

Well purple is the color of royalty. Does there need to be a reason for it to be in the castle?

Well purple is the color of royalty. Does there need to be a reason for it to be in the castle?

In BBS it was white-ish, blue-ish looking.

Edited June 8, 201610 yr by Keyblade master26

Purple could've also been a better color than others to show off their new shader.  This is essentially a playable demo for what we expect to see in KH3, its better to put your best foot forward and get people really hyped