display variable value in red when evaluation failed

src/SharpIDE.Godot/Features/CodeEditor/CustomSyntaxHighlighter.cs

@@ -304,6 +304,7 @@ public static class CachedColors
     public static readonly Color VariableBlue = new("9cdcfe");
     public static readonly Color Gray = new("a9a9a9");
     public static readonly Color Pink = new("c586c0");
+    public static readonly Color ErrorRed = new("da5b5a");
     
     public static readonly Color RazorComponentGreen = new("0b7f7f");
     public static readonly Color RazorMetaCodePurple = new("a699e6");

src/SharpIDE.Godot/Features/Debug_/Tab/SubTabs/ThreadsVariablesSubTab.DebuggerVariableCustomDraw.cs

@@ -34,6 +34,7 @@ public partial class ThreadsVariablesSubTab
 
         var variableValueDisplayColour = variable switch
         {
+            _ when variable.PresentationHint?.Attributes is { } attrs && (attrs & VariablePresentationHint.AttributesValue.FailedEvaluation) != 0 => CachedColors.ErrorRed,
             { Value: "null" } => CachedColors.KeywordBlue,
             { Value: "true" or "false" } => CachedColors.KeywordBlue,
             { Type: "string" or "char" } => CachedColors.LightOrangeBrown,