diff --git a/plot_transmission_timeline.py b/plot_transmission_timeline.py
index 0700396..19b781d 100755
--- a/plot_transmission_timeline.py
+++ b/plot_transmission_timeline.py
@@ -189,12 +189,19 @@ if __name__ == "__main__":
 
     host = host_subplot(111, axes_class=axisartist.Axes)
 
+    # create list fo color indices
     transmission_df["index"] = transmission_df.index
+    color_dict = dict()
+    i = 0
+    for cell_id in transmission_df["cellID"].unique():
+        if cell_id not in color_dict:
+            color_dict[cell_id] = i
+            i += 1
 
     cmap = matplotlib.cm.get_cmap("Set3")
-    for c in transmission_df["cellID"].unique():
-        bounds = transmission_df[["index", "cellID"]].groupby("cellID").agg(["min", "max"]).loc[c]
-        host.axvspan(bounds.min(), bounds.max(), alpha=0.3, color=cmap.colors[c])
+    for cell_id in transmission_df["cellID"].unique():
+        bounds = transmission_df[["index", "cellID"]].groupby("cellID").agg(["min", "max"]).loc[cell_id]
+        host.axvspan(bounds.min(), bounds.max(), alpha=0.3, color=cmap.colors[color_dict[cell_id]])
 
     plt.subplots_adjust()