diff --git a/stimuli/utils/plotting.py b/stimuli/utils/plotting.py
index 549bbad4..a145bb9f 100644
--- a/stimuli/utils/plotting.py
+++ b/stimuli/utils/plotting.py
@@ -52,13 +52,15 @@ def plot_stim(
             img = np.dstack([img, img, img])
             mask = np.dstack([mask, mask, mask])
 
-            if np.unique(mask).size > 10:
+            if np.unique(mask).size >= 20:
+                colormap = plt.cm.colors.ListedColormap(np.random.rand(mask.max()+1,3))
+            elif np.unique(mask).size > 10 and np.unique(mask).size < 20:
                 colormap = plt.cm.tab20
             else:
                 colormap = plt.cm.tab10
 
             for idx in np.unique(mask)[np.unique(mask) > 0]:
-                color = colormap.colors[idx % 19]
+                color = colormap.colors[idx]
                 color = np.reshape(color, (1, 1, 3))
                 img = np.where(mask == idx, color, img)
             ax.imshow(img)