diff --git a/packages/block-library/src/navigation/editor.scss b/packages/block-library/src/navigation/editor.scss
index 14db7a85b0b81c..ec1c1904130295 100644
--- a/packages/block-library/src/navigation/editor.scss
+++ b/packages/block-library/src/navigation/editor.scss
@@ -100,6 +100,18 @@
 	display: block;
 	position: static;
 	width: 100%;
+
+	// Colors need to work in both dark themes, and dark dropdown colors.
+	// This customization would be nice to retire in a refactor of the canvas appender button.
+	.block-editor-button-block-appender {
+		color: $white;
+		background: $gray-900;
+		padding: 0;
+		width: $button-size-small;
+		border-radius: $radius-block-ui;
+		margin-right: 0;
+		margin-left: auto;
+	}
 }
 
 // Hide when hovering.