+// darken(@main_alt_colour, 13.5%) > #cccccc
+// darken(@main_alt_colour, 33%) > #9a9a9a
+// darken(@main_alt_colour, 24%) > #b1b1b1
+// darken(@main_alt_colour, 27%) > #a9a9a9
+// darken(@main_alt_colour, 33.5%) > #999999
+// darken(@main_alt_colour, 40%) > #888888
+// darken(@main_alt_colour, 46.8%) > #777777
+// darken(@main_alt_colour, 53.5%) > #666666