Question

what colors of ink do color ink -jet printers use to produce a full range of colors? do the colors form by color addition or by color subtraction?

Answer 1

Ink works by subtracting colors from the white light that illuminates them. Each allows a fairly wide rainge of wavelengths to be reflected; the reflected light is not highly monochromatic. The colors look a lot different from the red, blue and green that are used in color addition. Frequent ink color choices are magenta, yellow and cyan. See
http://en.wikipedia.org/wiki/Subtractive_color
for more about how it works