Ah, Blue's magic didn't make her surroundings darker, actually... it was just that at the time of her sealing the blinding light back into her sword before shooting it out as a beam, the world seemed much darker than it had been before due to her eyesight (in particular, since I was writing as her, but it probably extended to everyone since it's a pretty natural reaction) having tried to adjust to the searingly bright surroundings from before. It's like, if you walk from a brightly lit room into a dark one, or stand in light and look into darkness, you can't see anything, but if you walk into the darkness and let your eyes adjust your surroundings will gradually seem brighter. It's the same thing that happens when you're blinded by headlights at night; your eyes try to adjust to the brightness of the headlights, and afterwards the night seems much darker than it had been a moment ago.
And yeah, it does need to be [I]a[/I] vampire's blood that comes into contact with the wound for his rapid regeneration to activate. As a matter of fact all of a vampire's abilities come from its blood, and the curse that permeates it; the vampiric blood is what keeps a vampire alive. That is also why a severed vampire limb would need to be continuously bathed in vampire blood for it to survive... a vampire's heart is the only part of it that can survive on non-vampiric blood, because it is what infuses normal blood with the curse, transmuting it into vampire blood. Different vampires also have varying strength depending on the dillution of their curse, or how many times it has been passed between individuals from the original vampires to the current recipient. The originals were almost incomparable to modern vampires... but I digress. Vampiric blood is infused with persistent life and facilitates accelerated healing; normal blood is not and does not do the same.