Returns the correct colour for a geological period.
Currently requires expansion to work with all periods.
The colours use the World Geological Map (Paris) colours, the global standard used at by the international commission for stratigraphy.
The rgb values in this chart were originally generated using Ogg's free TS creator to generate a chart, saved as an .svg, opened with Inkscape.
The template should be updated to use the values stated at http://www.purdue.edu/stratigraphy/charts/RGB.pdf Clowan:Dead link. Please be careful not to leave any spaces in the rgb() declaration.