diff --git a/tikz/3d-gradient-colored/3d-gradient-colored.png b/tikz/3d-gradient-colored/3d-gradient-colored.png
index 338f375..f1ab39c 100644
Binary files a/tikz/3d-gradient-colored/3d-gradient-colored.png and b/tikz/3d-gradient-colored/3d-gradient-colored.png differ
diff --git a/tikz/3d-gradient-colored/3d-gradient-colored.tex b/tikz/3d-gradient-colored/3d-gradient-colored.tex
index 0e39898..2182a97 100644
--- a/tikz/3d-gradient-colored/3d-gradient-colored.tex
+++ b/tikz/3d-gradient-colored/3d-gradient-colored.tex
@@ -2,7 +2,7 @@
 
 \usepackage[usenames,dvipsnames]{xcolor}
 \usepackage{pgfplots}
-\pgfplotsset{compat=1.11}
+\pgfplotsset{compat=1.13}
 \usetikzlibrary{arrows.meta}
 
 \begin{document}
diff --git a/tikz/ellipsoid/ellipsoid.png b/tikz/ellipsoid/ellipsoid.png
index 05b009d..76b2c9c 100644
Binary files a/tikz/ellipsoid/ellipsoid.png and b/tikz/ellipsoid/ellipsoid.png differ
diff --git a/tikz/ellipsoid/ellipsoid.tex b/tikz/ellipsoid/ellipsoid.tex
index b98b47b..b4057ee 100644
--- a/tikz/ellipsoid/ellipsoid.tex
+++ b/tikz/ellipsoid/ellipsoid.tex
@@ -38,7 +38,7 @@
         %xticklabels={,,},
         %yticklabels={,,}
     ]
-      \addplot3[surf] {-(x*x/16+y*y/4-1)};
+      \addplot3[surf, colormap name=viridis] {-(x*x/16+y*y/4-1)};
     \end{axis}
 \end{tikzpicture}
 \end{preview}
diff --git a/tikz/hypersurface-2/hypersurface-2.png b/tikz/hypersurface-2/hypersurface-2.png
index aa2671b..1bd29ad 100644
Binary files a/tikz/hypersurface-2/hypersurface-2.png and b/tikz/hypersurface-2/hypersurface-2.png differ
diff --git a/tikz/hypersurface-2/hypersurface-2.tex b/tikz/hypersurface-2/hypersurface-2.tex
index 658ad41..574a4ec 100644
--- a/tikz/hypersurface-2/hypersurface-2.tex
+++ b/tikz/hypersurface-2/hypersurface-2.tex
@@ -42,7 +42,7 @@
         %xticklabels={,,},
         %yticklabels={,,}
     ]
-      \addplot3[surf] {3*x*x-y*y-9*x+1};
+      \addplot3[surf, colormap name=viridis] {3*x*x-y*y-9*x+1};
     \end{axis}
 \end{tikzpicture}
 \end{preview}
diff --git a/tikz/hypersurface-3/hypersurface-3.png b/tikz/hypersurface-3/hypersurface-3.png
index 5186c9d..d9307e9 100644
Binary files a/tikz/hypersurface-3/hypersurface-3.png and b/tikz/hypersurface-3/hypersurface-3.png differ
diff --git a/tikz/hypersurface-3/hypersurface-3.tex b/tikz/hypersurface-3/hypersurface-3.tex
index 629e6da..98ff779 100644
--- a/tikz/hypersurface-3/hypersurface-3.tex
+++ b/tikz/hypersurface-3/hypersurface-3.tex
@@ -38,7 +38,7 @@
         %xticklabels={,,},
         %yticklabels={,,}
     ]
-      \addplot3[surf] {-3/25*x*x+1/25*y*y};
+      \addplot3[surf, colormap name=viridis] {-3/25*x*x+1/25*y*y};
     \end{axis}
 \end{tikzpicture}
 \end{preview}
diff --git a/tikz/hypersurface-order-2/hypersurface-order-2.png b/tikz/hypersurface-order-2/hypersurface-order-2.png
index 9e7e48d..87131f7 100644
Binary files a/tikz/hypersurface-order-2/hypersurface-order-2.png and b/tikz/hypersurface-order-2/hypersurface-order-2.png differ
diff --git a/tikz/hypersurface-order-2/hypersurface-order-2.tex b/tikz/hypersurface-order-2/hypersurface-order-2.tex
index b57fc5d..8198a45 100644
--- a/tikz/hypersurface-order-2/hypersurface-order-2.tex
+++ b/tikz/hypersurface-order-2/hypersurface-order-2.tex
@@ -44,7 +44,7 @@
     ]
       % if you want to use Wolfram|Alpha:
       % Plot3D[x*x-4*x*y+y*y+1, {x, -5, 5}, {y, -5, 5}]
-      \addplot3[surf] {x*x-4*x*y+y*y+1};
+      \addplot3[surf, colormap name=viridis] {x*x-4*x*y+y*y+1};
     \end{axis}
 \end{tikzpicture}
 \end{preview}