You don't say what version of Word you are using. In theory colours in Word
and Excel 2007 behave similarly, but in earlier versions, Excel's limited
colour palette was unlike anything in Word.

Regardless of that, I'm not sure exactly what you are having trouble with,
but it may help to know that, when  you have coloured one cell with your
chosen colour, all you have to do to get the same colour in other cells is
to place the cursor in the other cell and press F4 or Ctrl+Y to repeat the
command.