fix colors variable

Author: cldougl

plotly/tools.py

@@ -3061,7 +3061,7 @@ def __init__(self, hist_data, group_labels,
         self.start = []
         self.end = []
         if colors:
-            self.colors = 'colors'
+            self.colors = colors
         else:
             self.colors = [
                 "rgb(31, 119, 180)", "rgb(255, 127, 14)",