Darken/lighten a hex colour by the given amount Stolen from https://benjaminlmoore.wordpress.com/2014/03/18/guardian-data-blog-uk-elections/

darken_colour(hex_colour, amount = 0.15)

lighten_colour(hex_colour, amount = 0.15)

Arguments

hex_colour

strings e.g. "#345678"

amount

fraction to darken by. default 0.15

Value

darkened hex colours