First, make sure that "Print Color Patterns" is selected in Print Options. If the print is still black-and-white, do a printer self-test.
Here's how:
1) Turn the printer off
2) While holding down the form feed button, turn the printer on. Release the form feed button.
The printer should print lines of text in different colors. If it doesn't, the printer ribbon is probably not pushed down tight enough. Push the ribbon down FIRMLY. This is necessary to depress the detector switch below the ribbon that tells the printer that a color ribbon is present.