Sadness? Mystery? Depression? Loneliness? Dark?

Not always...

For me black is the mixture of all the colours, all the colours under the sky mix together to form black, still, it's different from all colours.

It tells me that many times we would end up being different even after having the qualities of people around us, people who helped us build ourselves because we are all different, I am 'I' and you are 'YOU'

It accepts the difference of all the colours to form itself.

Therefore for me, black is accepting one's differences and accepting oneself.