diff --git a/core/language/en-GB/Docs/PaletteColours.multids b/core/language/en-GB/Docs/PaletteColours.multids
index 98addbf85..636d2d3b1 100644
--- a/core/language/en-GB/Docs/PaletteColours.multids
+++ b/core/language/en-GB/Docs/PaletteColours.multids
@@ -65,6 +65,9 @@ sidebar-tab-foreground-selected: Sidebar tab foreground for selected tabs
 sidebar-tab-foreground: Sidebar tab foreground
 sidebar-tiddler-link-foreground-hover: Sidebar tiddler link foreground hover
 sidebar-tiddler-link-foreground: Sidebar tiddler link foreground
+testcase-accent-level-1: Testcase accent colour with no nesting
+testcase-accent-level-2: Testcase accent colour with 2nd level nesting
+testcase-accent-level-3: Testcase accent colour with 3rd level nesting or higher
 site-title-foreground: Site title foreground
 static-alert-foreground: Static alert foreground
 tab-background-selected: Tab background for selected tabs
diff --git a/core/palettes/Vanilla.tid b/core/palettes/Vanilla.tid
index 4c660e912..c7c800046 100644
--- a/core/palettes/Vanilla.tid
+++ b/core/palettes/Vanilla.tid
@@ -95,6 +95,9 @@ table-footer-background: #a8a8a8
 table-header-background: #f0f0f0
 tag-background: #ec6
 tag-foreground: #ffffff
+testcase-accent-level-1: #84C5E6
+testcase-accent-level-2: #E3B740
+testcase-accent-level-3: #5FD564
 tiddler-background: <<colour background>>
 tiddler-border: <<colour background>>
 tiddler-controls-foreground-hover: #888888
diff --git a/themes/tiddlywiki/vanilla/base.tid b/themes/tiddlywiki/vanilla/base.tid
index 89b5c9525..95b7a1960 100644
--- a/themes/tiddlywiki/vanilla/base.tid
+++ b/themes/tiddlywiki/vanilla/base.tid
@@ -3232,6 +3232,18 @@ span.tc-translink > a:first-child {
 	border-radius: 6px;
 }
 
+.tc-testcase-wrapper {
+	background-color: <<colour testcase-accent-level-1>>;
+}
+
+.tc-testcase-wrapper .tc-testcase-wrapper {
+	background-color: <<colour testcase-accent-level-2>>;
+}
+
+.tc-testcase-wrapper .tc-testcase-wrapper .tc-testcase-wrapper {
+	background-color: <<colour testcase-accent-level-3>>;
+}
+
 .tc-testcase-header {
 	font-weight: normal;
 	margin: 0.5em 0;