5.3 Colours

5.3.1 Using the Brewer palettes:

5.3.2 Legend title

scale_colour_brewer() is also a convenient place to change the legend title:

Note the \n inside the new legend title - new line.

5.3.3 Choosing colours manually

Use words:

Or HEX codes (either from http://colorbrewer2.org/ or any other resource):

Note that http://colorbrewer2.org/ also has options for Colourblind safe and Print friendly.