The ratios vary from person to person, but in general there are more red and green receptors then blue ones. Some people are born with different ratios of receptors, and they suffer from colour blindness, so they see hues of colours differently. Colour blindness affects one in 10 men, and one in 100 women. The severity of the condition varies, so much so that some people might not even be aware that they suffer from it. Total colour blindness, where no cones are present at all, is extremely rare.
Monitors reproduce different colours by combining red, green and blue in varying proportions.
This way they attempt to reproduce the same relative response in the cones as the real colour would. Because the colours of the filters in the monitor don't match the cones' most responsive colours, a small margin of error creeps in. A monitor will therefore never be able to perfectly reproduce something we see with our own eyes. The colour space of an RGB monitor doesn't cover the whole range of the eye. That said, monitors produce a far greater range of colours than the CMYK printing process used in magazines.