Function: facemenu-set-background

Set the background COLOR of the region or next character typed.
This command reads the color in the minibuffer.

If the region is active (normally true except in Transient Mark mode)
and there is no prefix argument, this command sets the region to the
requested face.

Otherwise, this command specifies the face for the next character
inserted. Moving point or switching buffers before
typing a character to insert cancels the specification.