Color Scheme for black color

[musingh1]

Feature Request

We have a scenario where we need a Label to have a black background

Problem description

This does not exist in the current colorSchemes

Proposed solution

Can we please add a color scheme for black color so that I can use it with Label component in my use case.

Also, the color black exported from siteVariables is actually grey and not full black.
black: naturalColors.grey[900],
Can we please export fullBlack : #000 in siteVariables as well.

MVP