In my opinion....

Black and white photograph more scary by removing/not showing colour, changing our view angle of sight from wide into narrow, forces the photographer and the viewer to concentrate on the subject, on the light, and on contrast also dark color increase the feeling anxiety, depression, sadness, isolation or anything melancholic.

it's scary because black and white photograph showing more our thought being curiousity to unknown object in dim/dark places, not in bad thing because it's within our DNA, our survival instict since humanity in beginning of time from struggle for staying alive it night from predator into discovering the unknown of space and beyond.

human always terifying against the unknown in the dark and yet still have a feeling to try to find out as its insecurity of being not being safe in which still lurking inside until it soon be resolved.. it's the curiousity, trill and mystery that audience love while watching horror film , it is the color that showing negative space in ying and yang in taoism... it is like adam and eve's story when they feel curiosity by eating forbidden fruit in the heaven just want to find out how to know how is good and how is evil or how to be a god itself, in the end, adam and eve's also snake get banished from heaven by God because snake know how to tricked human curiousity.

in short.. black and white photograph is authentic, showing the audience sense to explore your photograph deeply, adding mystery into your photograph and touching our deepest curiousity within ourselves, which is great to convey our emotion in photograhy.