Implement a colourblind-safe scheme of colours for the a-priori plots

[PTierz]

Summary

Following these suggestions in Twitter (Tweet#1, Tweet#2), it would be desirable to have a colourblind-safe scheme of colours to display the single-criterion analogy values in the plots generated with the --plot-apriori flag. Possible options may be found in the ColorBrewer website.

Acceptance criteria

• pyvolcans Fuego --apriori Villarrica Llaima Pacaya Reventador Tungurahua --plot_apriori plots bar colours that are colourblind safe