The rainbow (a.k.a. jet) colour map is in a scientific context extremely problematic. It should not be used in science any longer as it is difficult to read and distorts the data significantly:
The rainbow (a.k.a. jet) colour map...
See below for references.
The figure shows the colour map with low gradient ripples to indicate how it represents low-contrast regions in different locations of the colorbar, and a plot of the lightness difference, dE, indicating better perceptual-uniformity the flatter the curve.
Diagnostics performed after Kovesi, P. (2015), Good colour maps: How to design them, CoRR, abs/1509.03700 and based on MatLab scripts from https://www.peterkovesi.com/matlabfns/index.html#colour .
Thyng, K.M., C.A. Greene, R.D. Hetland, H.M. Zimmerle, and S.F. DiMarco, 2016, True colors of oceanography: Guidelines for effective and accurate colormap selection, Oceanography, 29(3), 9–13. http://dx.doi.org/10.5670/oceanog.2016.66
D. Borland and R.M. Tailor, “Rainbow Color Map (still) considered harmful,” IEEE Computer Society, vol. 07, 2007, p. 14-17.
Light and P.J. Bartlein, “The End of the Rainbow? Color Schemes for Improved Data Graphics,” EOS Trans. Amer. Geophysical Union, vol. 85, no. 40, 2004, p. 385.
C. Ware, Information Visualization: Perception for Design, 2nd ed., Morgan Kaufmann, 2004.
B.E. Rogowitz and L.A. Treinish, “Data Visualization: The End of the Rainbow,” IEEE Spectrum, vol. 35, no. 12, 1998, pp. 52-59.
E.R. Tufte, Visual Explanations, Graphics Press, 1997.
B.E. Rogowitz and L.A. Treinish, “How Not to Lie with Visualization,” Computers in Physics, vol. 10, no. 3, 1996, pp. 268-273.
C.G. Healey, “Choosing Effective Colors for Data Visualization, Proc. IEEE Visualization, IEEE CS Press, 1996, pp. 263-270.
P. Rheingans, “Color, Change, and Control for Quantitative Data Display,” Proc. IEEE Visualization, IEEE CS Press, 1992, pp. 252-259.
C. Ware, “Color Sequences for Univariate Maps: Theory, Experiments, and Principles,” IEEE Computer Graphics and Applications, vol. 8, no.5, 1988, pp. 41-49.
S.M. Pizer and J.B. Zimmerman, “Color Display in Ultrasonography,” Ultrasound in Medicine and Biology, vol. 9, no. 4, 1983, pp. 331-345. §