diff --git a/.github/workflows/cache.yml b/.github/workflows/cache.yml
index 1a67a4ce..f1c7c712 100644
--- a/.github/workflows/cache.yml
+++ b/.github/workflows/cache.yml
@@ -11,9 +11,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Setup Anaconda
-        uses: conda-incubator/setup-miniconda@v2
+        uses: conda-incubator/setup-miniconda@v3
         with:
           auto-update-conda: true
           auto-activate-base: true
@@ -39,13 +39,13 @@ jobs:
         run: |
           jb build lectures --path-output ./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         if: failure()
         with:
           name: execution-reports
           path: _build/html/reports
       - name: Upload "_build" folder (cache)
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: build-cache
           path: _build
\ No newline at end of file
diff --git a/.github/workflows/execution.yml b/.github/workflows/execution.yml
index 35e3c926..2d5f5493 100644
--- a/.github/workflows/execution.yml
+++ b/.github/workflows/execution.yml
@@ -14,7 +14,7 @@ jobs:
         python-version: ["3.11"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - uses: conda-incubator/setup-miniconda@v2
         with:
           auto-update-conda: true
@@ -41,7 +41,7 @@ jobs:
         shell: bash -l {0}
         run: jb build lectures --path-output=./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         if: failure()
         with:
           name: execution-reports
@@ -56,8 +56,8 @@ jobs:
         python-version: ["3.11"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
-      - uses: conda-incubator/setup-miniconda@v2
+        uses: actions/checkout@v4
+      - uses: conda-incubator/setup-miniconda@v3
         with:
           auto-update-conda: true
           python-version: ${{ matrix.python-version }}
@@ -73,7 +73,7 @@ jobs:
         shell: bash -l {0}
         run: jb build lectures --path-output=./ -W --keep-going
       - name: Upload Execution Reports
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         if: failure()
         with:
           name: execution-reports
diff --git a/.github/workflows/linkcheck.yml b/.github/workflows/linkcheck.yml
index 79f0578b..677a1967 100644
--- a/.github/workflows/linkcheck.yml
+++ b/.github/workflows/linkcheck.yml
@@ -16,9 +16,9 @@ jobs:
         python-version: ["3.11"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Setup Anaconda
-        uses: conda-incubator/setup-miniconda@v2
+        uses: conda-incubator/setup-miniconda@v3
         with:
           auto-update-conda: true
           auto-activate-base: true
@@ -27,7 +27,7 @@ jobs:
           environment-file: environment.yml
           activate-environment: quantecon
       - name: Download "build" folder (cache)
-        uses: dawidd6/action-download-artifact@v2
+        uses: dawidd6/action-download-artifact@v3
         with:
           workflow: cache.yml
           branch: main
@@ -37,7 +37,7 @@ jobs:
         shell: bash -l {0}
         run: jb build lectures --path-output=./ --builder=custom --custom-builder=linkcheck
       - name: Upload Link Checker Reports
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         if: failure()
         with:
           name: linkcheck-reports
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index ae3266cc..d0f99f4c 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -9,9 +9,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Setup Anaconda
-        uses: conda-incubator/setup-miniconda@v2
+        uses: conda-incubator/setup-miniconda@v3
         with:
           auto-update-conda: true
           auto-activate-base: true
@@ -39,7 +39,7 @@ jobs:
         shell: bash -l {0}
         run: pip list
       - name: Download "build" folder (cache)
-        uses: dawidd6/action-download-artifact@v2
+        uses: dawidd6/action-download-artifact@v4
         with:
           workflow: cache.yml
           branch: main
@@ -79,7 +79,7 @@ jobs:
           publish_dir: _build/html/
           cname: python-advanced.quantecon.org
       - name: Upload "_build" folder (cache)
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: build-cache
           path: _build
diff --git a/environment.yml b/environment.yml
index 6aa0c8ce..e326c739 100644
--- a/environment.yml
+++ b/environment.yml
@@ -3,7 +3,7 @@ channels:
   - default
 dependencies:
   - python=3.11
-  - anaconda=2023.09
+  - anaconda=2024.02
   - pip
   - pip:
     - jupyter-book==0.15.1
diff --git a/lectures/smoothing_tax.md b/lectures/smoothing_tax.md
index c9e49bd2..a265a4f9 100644
--- a/lectures/smoothing_tax.md
+++ b/lectures/smoothing_tax.md
@@ -607,14 +607,13 @@ class TaxSmoothingExample:
 
         fig, ax = plt.subplots()
         ax.set_title('Cumulative return path (complete markets)')
-        line1 = ax.plot(np.arange(N), self.RT_path)[0]
+        line1 = ax.plot(np.arange(N), self.RT_path, color='blue')[0]
         c1 = line1.get_color()
         ax.set_xlabel('Periods')
         ax.set_ylabel('Cumulative return', color=c1)
 
         ax_ = ax.twinx()
-        ax_._get_lines.prop_cycler = ax._get_lines.prop_cycler
-        line2 = ax_.plot(np.arange(N), self.g_path, ls='--')[0]
+        line2 = ax_.plot(np.arange(N), self.g_path, ls='--', color='green')[0]
         c2 = line2.get_color()
         ax_.set_ylabel('Government expenditures', color=c2)