using System;

public class Program

{

    public static void Main()

    {

        var source = "anytext[Source1].[anytext:Column1:anytext]anytext";

        var src1 = "Source1";

        var dest1 = "ABC";

        var src2 = "Column1";

        var dest2 = "Col1";

​

        var result = source.Replace("[" + src1 + "]", "[" + dest1 +"]").Replace(":" + src2 + ":", ":" + dest2 +":");

        Console.WriteLine(result);

    }

}