diff --git a/static/colors.css b/static/colors.css
index bba38e1..d3bf14c 100644
--- a/static/colors.css
+++ b/static/colors.css
@@ -44,8 +44,6 @@
     --alert-warning: #ffaf00;
     --alert-caution: #ff5f5f;
 
-    --alert-custom-default: #c0c0c0;
-
     --ipynb-bg-error: rgba(255, 0, 0, 0.1);
 }
 
@@ -99,8 +97,6 @@
         --alert-warning: #bf8700;
         --alert-caution: #cf222e;
 
-        --alert-custom-default: #404040;
-
         --ipynb-bg-error: rgba(255, 0, 0, 0.1);
     }
 }
diff --git a/static/markdown.css b/static/markdown.css
index b8da31a..b2a295f 100644
--- a/static/markdown.css
+++ b/static/markdown.css
@@ -149,12 +149,12 @@ blockquote {
     vertical-align: text-bottom;
     fill: currentColor;
 }
-/* default style for custom markers (Obsidian Callout style) */
+/* default style for unconfigured custom markers (Obsidian Callout style) */
 .markdown-alert {
-    border-left: .25rem solid var(--alert-custom-default);
+    border-left: .25rem solid var(--alert-note);
 }
 .markdown-alert .markdown-alert-title {
-    color: var(--alert-custom-default);
+    color: var(--alert-note);
 }
 /* default styles for GitHub style markers */
 .markdown-alert-note {
diff --git a/tests/rendering/markdown-additional.md b/tests/rendering/markdown-additional.md
index 8bba8cb..5558ef0 100644
--- a/tests/rendering/markdown-additional.md
+++ b/tests/rendering/markdown-additional.md
@@ -67,13 +67,15 @@ This paragraph has a red background color.{style=background-color:red}
 
 ### With a custom title
 
-> [!NOTE] Foo bar
-> 'Note' with a custom title
+> [!TIP] Foo bar
+> 'Tip' with a custom title
 
 ### Using custom markers ([Obsidian Callout](https://help.obsidian.md/Editing+and+formatting/Callouts) style)
 
 > [!CUSTOM]
-> Something more special
+> Set custom icon and color for any marker
+>
+> If unconfigured, it's styled like 'Note'
 
 > [!fOoBaR]
 > The marker is case-insensitive and turns into Title Case