diff --git a/docs/notebooks/density_and_public_transportation.ipynb b/docs/notebooks/density_and_public_transportation.ipynb
index 3ffa1b1..170da81 100644
--- a/docs/notebooks/density_and_public_transportation.ipynb
+++ b/docs/notebooks/density_and_public_transportation.ipynb
@@ -245,9 +245,7 @@
     "jc = JenksCaspall(\n",
     "    zones_interpolated[\"Total Population + Worker Population Density\"].fillna(0), k=10\n",
     ")\n",
-    "colors = []\n",
-    "for color in jc.yb:\n",
-    "    colors.append(Viridis_20.colors[color])\n",
+    "colors = numpy.array(Viridis_20.colors)[jc.yb]\n",
     "layer.get_fill_color = numpy.uint8(colors)\n",
     "\n",
     "Map(layers=[layer])"
@@ -470,9 +468,7 @@
     "jc = JenksCaspall(\n",
     "    zones_interpolated[\"Total Population + Worker Population Density\"], k=10\n",
     ")\n",
-    "colors = []\n",
-    "for color in jc.yb:\n",
-    "    colors.append(Viridis_20.colors[color])\n",
+    "colors = numpy.array(Viridis_20.colors)[jc.yb]\n",
     "layer.get_fill_color = numpy.uint8(colors)\n",
     "layers = [layer]\n",
     "for route in network.routes:\n",
@@ -648,13 +644,12 @@
    "outputs": [],
    "source": [
     "from mapclassify import Quantiles\n",
+    "import numpy\n",
     "\n",
     "zones_interpolated[\"Accessibility w/in 15 minutes\"] = tdf.T.sum()\n",
     "layer = SolidPolygonLayer.from_geopandas(zones_interpolated, opacity=0.1)\n",
     "jc = Quantiles(zones_interpolated[\"Accessibility w/in 15 minutes\"], k=10)\n",
-    "colors = []\n",
-    "for color in jc.yb:\n",
-    "    colors.append(Viridis_20.colors[color])\n",
+    "colors = numpy.array(Viridis_20.colors)[jc.yb]\n",
     "layer.get_fill_color = numpy.uint8(colors)\n",
     "layers = [layer]\n",
     "\n",