Maybe,
CTRL-1, to bring up Format cells dialog
then either CTRL-TAB or CTRL-SHIFT-TAB as required until the 'Patterns' tab is active
ALT-C
arrow to the colour you want, SPACE to select it
TAB two times to activate the OK, then RETURN to complete
And, btw, after you've done one, F4 can be used to repeat
HTH, Fazza