The Fabio Crameri Scientific Colour Maps are widely popular, with implementations of the palettes in R, Fortran, and others. Popular for good reason, the palettes are colorblind-friendly, retain representational clarity in greyscale, and are generally aesthetically pleasing.
This tool provides a convenience wrapper around D3js's colour interpolation functions, preloaded with colour palettes in Javascript format, based on this Gist, as well as implementation for use in data visualization tools with manual color value specification (e.g., Microsoft Excel, ArcGIS, and Tableau to name a few). To begin, select the number of categories and the color palette you'd like to use.