use default colors in one sankey mock

Author: alexcjohnson

test/image/baselines/sankey_energy_dark.png

@@ -71,56 +71,7 @@
                     "UK land based bioenergy",
                     "Wave",
                     "Wind"
-                ],
-                "color": [
-                    "rgba(31, 119, 180, 0.8)",
-                    "rgba(255, 127, 14, 0.8)",
-                    "rgba(44, 160, 44, 0.8)",
-                    "rgba(214, 39, 40, 0.8)",
-                    "rgba(148, 103, 189, 0.8)",
-                    "rgba(140, 86, 75, 0.8)",
-                    "rgba(227, 119, 194, 0.8)",
-                    "rgba(127, 127, 127, 0.8)",
-                    "rgba(188, 189, 34, 0.8)",
-                    "rgba(23, 190, 207, 0.8)",
-                    "rgba(31, 119, 180, 0.8)",
-                    "rgba(255, 127, 14, 0.8)",
-                    "rgba(44, 160, 44, 0.8)",
-                    "rgba(214, 39, 40, 0.8)",
-                    "rgba(148, 103, 189, 0.8)",
-                    "rgba(140, 86, 75, 0.8)",
-                    "rgba(227, 119, 194, 0.8)",
-                    "rgba(127, 127, 127, 0.8)",
-                    "rgba(188, 189, 34, 0.8)",
-                    "rgba(23, 190, 207, 0.8)",
-                    "rgba(31, 119, 180, 0.8)",
-                    "rgba(255, 127, 14, 0.8)",
-                    "rgba(44, 160, 44, 0.8)",
-                    "rgba(214, 39, 40, 0.8)",
-                    "rgba(148, 103, 189, 0.8)",
-                    "rgba(140, 86, 75, 0.8)",
-                    "rgba(227, 119, 194, 0.8)",
-                    "rgba(127, 127, 127, 0.8)",
-                    "rgba(188, 189, 34, 0.8)",
-                    "rgba(23, 190, 207, 0.8)",
-                    "rgba(31, 119, 180, 0.8)",
-                    "rgba(255, 127, 14, 0.8)",
-                    "rgba(44, 160, 44, 0.8)",
-                    "rgba(214, 39, 40, 0.8)",
-                    "rgba(148, 103, 189, 0.8)",
-                    "magenta",
-                    "rgba(227, 119, 194, 0.8)",
-                    "rgba(127, 127, 127, 0.8)",
-                    "rgba(188, 189, 34, 0.8)",
-                    "rgba(23, 190, 207, 0.8)",
-                    "rgba(31, 119, 180, 0.8)",
-                    "rgba(255, 127, 14, 0.8)",
-                    "rgba(44, 160, 44, 0.8)",
-                    "rgba(214, 39, 40, 0.8)",
-                    "rgba(148, 103, 189, 0.8)",
-                    "rgba(140, 86, 75, 0.8)",
-                    "rgba(227, 119, 194, 0.8)",
-                    "rgba(127, 127, 127, 0.8)"]
+                ]
             },
             "link": {
                 "source": [