It is time to clamp down on the use of misleading rainbow colour scales that are increasingly pervading the literature and the media (see Accurate graphics are key to clear communication of scientific results to other researchers and the public — an issue that is becoming ever more important.

Aside from the challenge they pose for colour-blind readers (S. C. Allred et al. Nature 510, 340; 2014), spectral-type colour palettes can introduce false perceptual thresholds in the data (or hide genuine ones); they may also mask fine detail in the data (D. Borland and R. M. Taylor Comput. Graph. Appl. 27, 14–17; 2007). These palettes have no unique perceptual ordering, so they can de-emphasize data extremes by placing the most prominent colour near the middle of the scale.

These issues can have profound consequences: for example, changing to a non-rainbow colour scale improved diagnostic accuracy for heart disease (M. Borkin et al. IEEE Trans. Vis. Comput. Graph. 17, 2479–2488; 2011).

Journals should not tolerate poor visual communication, particularly because better alternatives to rainbow scales are readily available (see, for example, and We urge all journals to stipulate in their guidelines that graphics must convey accurate and accessible information.