Colour for column selection in debugging mode added to high contrast theme....

Colour for column selection in debugging mode added to high contrast theme. Amended yellow frame column selection to stand out in light themes.

src/vs/workbench/parts/debug/browser/media/debug.contribution.css

@@ -17,7 +17,7 @@
 }
 
 .monaco-editor .debug-top-stack-frame-column {
-	background: rgba(255, 200, 0, 0.2);
+	background: rgba(255, 200, 0, 0.7);
 }
 
 .monaco-editor .debug-focused-stack-frame-line {
@@ -244,4 +244,8 @@
 .hc-black .monaco-editor .debug-top-stack-frame-line {
 	background: rgba(255, 246, 0, .87);
 	mix-blend-mode: lighten; /* Preserves text selection's contrast */
+}
+
+.hc-black .monaco-editor .debug-top-stack-frame-column {
+	outline: 2px solid #ff0000;
 }
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