my powermac G5 will only print in one colour and black, how do i fix this?

Please help...

my mac is only printing in one colour - blue, and black. My partner's dyslexia tutor changed some settings "somewhere" as the black ink was running low and my partner had his finals coming up and didn't have time to get a new black cartridge. So his coursework printed in blue, to save black ink, but we can't get it back to normal to print any photo's etc. I remember seeing a colour wheel but don't know anymore ......