Soulmate AU where you can't see color until you touch your soulmate for the first time.
Elaboration: Your soulmate will appear a little bit brighter than everything else around you for the 24 hours directly after touching your soulmate so you can find them in case you bumped into them in a crowd of people.
When your soulmate dies, your colors become faded, or are almost gone; however, if your soulmate dies by suicide or they're murdered by you, then you'll go completely blind.
Imagine you're married to your soulmate, and you're just reading while your soulmate goes shopping when suddenly everything fades, or maybe you're watching TV and out of nowhere, everything goes black.
EXAMPLE SHORT STORY:
TBC