Changing color mode from Grayscale to CMYK or RGB

I have scanned a black & white document and am now wanting to add color. When I click on image-mode the only options I have are grayscale & bitmap. How am I able to change the color to CMYK or RGB to be able to add color?

Thanks.

Change to Greyscale and THEN to RGB

Change to grayscale first. The CMYK and RGB options should then be available.