Even with Futures numerous girlfriends, numerous people he’d had relationships with, his world was still grey. He still saw everything in black and white, despite thinking every time that he had met his soul mate. The idea of soul mates was odd, even in the spirit world, the idea that one person (or sometimes more than one person) would be perfect for you still occasionally made future feel weird. He’s been here for years, centuries probably (time seems to slow down or speed up whenever it feels like it) and the soul mate colour thing still isn’t entirely normal for him.
Then he meets her. She doesn’t think she is perfect, but to Future she’s the most perfect person ever. Carrie, only recently arrived, and already turning everything upside down. The three ghosts have changed their way of working, and she’s changed Futures world. For the first time he is seeing everything in colour. He can see the colour of Presents jumper (not what he’d have chosen, if he’d met his soul mate years before even if he was in denial about that fact), see the colour of the kings robes, and see the drab walls of the office. He can see everything, and loves it. He loves Carrie for opening his eyes, and loves understanding exactly what the deal with colours is.