Sir

Chris Miall, in Correspondence (“Readers see red over low-impact graphics” Nature 455, 147; 2007), points out that a small but significant proportion of the population have difficulty distinguishing colours in red/green images. For this reason, several journals now require images to be published in other colour pairs, the most common being magenta and yellow.

However, when using colours to evaluate protein co-localization, for example, as is now common in confocal microscopy data, some of the alternative colour schemes just do not work. Magenta and yellow in overlay produce 'almost white' — virtually indistinguishable from the yellow in tiny images.

Red and green, the standard colour pair, produce yellow when overlaid, and this is very easy to interpret. I suggest that journals continue to publish these images in red/green, but that they make alternatively coloured images available online as supplementary information for readers who have impaired colour vision.