Match behaviour and coloring of Cake in GitLab CI log

In GitLabCILog, use the same color palette as used by Cake on the local console.
Write "Error" and "Fatal" messages to the error stream instead of the output stream.

src/Cake.GitLabCI.Module/GitLabCILog.cs

@@ -1,6 +1,8 @@
 using System;
+
 using Cake.Core;
 using Cake.Core.Diagnostics;
+
 using JetBrains.Annotations;
 
 namespace Cake.AzurePipelines.Module
@@ -14,8 +16,12 @@ public class GitLabCILog : ICakeLog
         private static class AnsiEscapeCodes
         {
             public static readonly string Reset = string.Format(FORMAT, 0);
-            public static readonly string ForegroundRed = string.Format(FORMAT, 31);
+            public static readonly string ForegroundWhite = string.Format(FORMAT, 97);
             public static readonly string ForegroundYellow = string.Format(FORMAT, 33);
+            public static readonly string ForegroundLightGray = string.Format(FORMAT, 37);
+            public static readonly string ForegroundDarkGray = string.Format(FORMAT, 90);
+            public static readonly string BackgroundMagenta = string.Format(FORMAT, 45);
+            public static readonly string BackgroundRed = string.Format(FORMAT, 41);
 
             private const string FORMAT = "\u001B[{0}m";
         }
@@ -49,19 +55,27 @@ public void Write(Verbosity verbosity, LogLevel level, string format, params obj
 
             // Use colored output for log messages on GitLab CI
             // For reference, see https://docs.gitlab.com/ee/ci/yaml/script.html#add-color-codes-to-script-output
+            // For the colors, mostly match the colors used by Cake, see https://github.com/cake-build/cake/blob/ed612029b92f5da2b6cbdfe295c62e6b99a2963d/src/Cake.Core/Diagnostics/Console/ConsolePalette.cs#L34C17-L34C17
+            // Not however, that the GitLab Web UI seems to render some colors the same (e.g. white and dark gray
             switch (level)
             {
                 case LogLevel.Fatal:
+                    _console.WriteErrorLine($"{AnsiEscapeCodes.BackgroundMagenta}{AnsiEscapeCodes.ForegroundWhite}{level}: {string.Format(format, args)}{AnsiEscapeCodes.Reset}");
+                    break;
                 case LogLevel.Error:
-                    _console.WriteLine($"{AnsiEscapeCodes.ForegroundRed}{level}: {string.Format(format, args)}{AnsiEscapeCodes.Reset}");
+                    _console.WriteErrorLine($"{AnsiEscapeCodes.BackgroundRed}{AnsiEscapeCodes.ForegroundWhite}{level}: {string.Format(format, args)}{AnsiEscapeCodes.Reset}");
                     break;
                 case LogLevel.Warning:
                     _console.WriteLine($"{AnsiEscapeCodes.ForegroundYellow}{level}: {string.Format(format, args)}{AnsiEscapeCodes.Reset}");
                     break;
                 case LogLevel.Information:
+                    _console.WriteLine($"{level}: {string.Format(format, args)}");
+                    break;
                 case LogLevel.Verbose:
+                    _console.WriteLine($"{AnsiEscapeCodes.ForegroundLightGray}{level}: {string.Format(format, args)}{AnsiEscapeCodes.Reset}");
+                    break;
                 case LogLevel.Debug:
-                    _console.WriteLine($"{level}: {string.Format(format, args)}");
+                    _console.WriteLine($"{AnsiEscapeCodes.ForegroundDarkGray}{level}: {string.Format(format, args)}{AnsiEscapeCodes.Reset}");
                     break;
                 default:
                     throw new ArgumentOutOfRangeException(nameof(level), level, null);