Further reading
To understand the harmful implications of the rainbow color map, the interested reader can take a look at the academic paper Rainbow Color Map (Still) Considered Harmful, Borland and Taylor, IEEE Journal of Computer Graphics and Applications (Vol. 27, Issue 2). There are several websites that provide very useful resources for aesthetics in data visualization. The eagereyes.org website has a set of nice articles on issues ranging over design, aesthetics, and colors.