You see the world in black and white, until you meet your soulmate, then you can see everything in colour. But there could also be drawbacks. You could know when your soulmate is dieing as the colour could start to fade. Or maybe, when your soulmate dies, everything goes back to shades. Or, (this idea is actually mine) you keep your vision, when your soulmate dies, but are haunted by the fact that they gave you such an amazing gift, and now they are gone, they no longer get to witness it themselves, and everywhere you look you are reminded of them.