Is it necessary for both black & color cartridges to have ink with HP 1400 Printer/Scanner

I am a user of HP 1400 Printer cum Scanner which provides two slots for

one black and one color cartridge.
If the color cartridge has dried up and I am urgently in need of
printing out a document in black, can I print in black keeping the
exhasted color cartridge in the cradle? Have I to press the Black
button on the Printer for starting the print operation?
Similarly if the black cartridge has dried up, can I print in color,
keeping the exhausted black cartridge in the cradle as a dummy? Have I
to press the Color Button on the Printer to start operation?
Why doesn't HP provide a Manual of instructions for handling different
situations of this type?

P. Jayant