A logger extension to add background colored lines to Serilog

SerilogColoredLines.cs

using System;
using System.Collections.Generic;
using Serilog;
using Serilog.Sinks.SystemConsole.Themes;

namespace main1
{
    static class LoggerExtensions
    {
        public const string BackgroundBlack    = "\u001b[40m";
        public const string BackgroundRed      = "\u001b[41m";
        public const string BackgroundGreen    = "\u001b[42m";
        public const string BackgroundYellow   = "\u001b[43m";
        public const string BackgroundBlue     = "\u001b[44m";
        public const string BackgroundMagenta  = "\u001b[45m";
        public const string BackgroundCyan     = "\u001b[46m";
        public const string BackgroundWhite    = "\u001b[47m";
        public const string BackgroundBrightBlack      = "\u001b[40;1m";
        public const string BackgroundBrightRed        = "\u001b[41;1m";
        public const string BackgroundBrightGreen      = "\u001b[42;1m";
        public const string BackgroundBrightYellow     = "\u001b[43;1m";
        public const string BackgroundBrightBlue       = "\u001b[44;1m";
        public const string BackgroundBrightMagenta    = "\u001b[45;1m";
        public const string BackgroundBrightCyan       = "\u001b[46;1m";
        public const string BackgroundBrightWhite      = "\u001b[47;1m";

        public static List<int> AllIndexesOf(this string str, string value)
        {
            if (String.IsNullOrEmpty(value))
                throw new ArgumentException("the string to find may not be empty", "value");
            List<int> indexes = new List<int>();
            for (int index = 0; ; index += value.Length)
            {
                index = str.IndexOf(value, index);
                if (index == -1)
                    return indexes;
                indexes.Add(index);
            }
        }
        public static void BkColor(
          this ILogger logger,
          string messageTemplate,
          params object[] args)
        {
            // Get the color they chose
            string CurrentColor = (string)args[args.GetLength(0)-1];

            // Get rid of the color parameter now as it will break the Serilog parser
            args[args.GetLength(0)-1] = "";  

            // Prepend our color code to every argument (tested with strings and numbers)
            for (int i = 0; i < args.GetLength(0); i++)
            {
                args[i] = CurrentColor + args[i];
            }

            // Find all the arguments looking for the close bracket
            List<int> indexes = messageTemplate.AllIndexesOf("}");
            int iterations = 0;
            // rebuild messageTemplate with our color-coded arguments
            // Note: we have to increase the index on each iteration based on the previous insertion of
            // a color code
            foreach (var i in indexes)
            {
                messageTemplate = messageTemplate.Insert(i + 1 + (iterations++ * CurrentColor.Length), CurrentColor);
            }

            // Prefix the entire message template with color code
            string bkg = CurrentColor + messageTemplate;

            // Log it with a context
            logger.ForContext("IsImportant", true)
              .Information(bkg, args);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
            .MinimumLevel.Debug()
            .WriteTo.Async(a => a.Console(theme: AnsiConsoleTheme.Code))
            .CreateLogger();

            Log.Information("Hello, Async Serilog!");
            Log.Fatal("This is really bad!");
            Log.Logger.BkColor("Hello, {Name}! How are you {Today}? Pi is {Pi}", "World", "Today", 3.14159,LoggerExtensions.BackgroundBrightRed);
            Log.Logger.BkColor("Hello World", LoggerExtensions.BackgroundBrightGreen);
            Log.Logger.BkColor("Hello World. Today is {date}", DateTime.Now, LoggerExtensions.BackgroundBrightMagenta);
            Log.CloseAndFlush();
            Console.ReadKey();
        }
    }
}