Simple console application that changes text color based on user input
Review

Whitespace
Use whitespace between the method name and opening parenthesis: Main (string[] args) instead of Main(string[] args). The same convention applies to statements such as while: while (Continue) instead of while(Continue). And also to curly braces: new string[4] { instead of new string[4]{.



New Line
Prefer using the new line of the system over a fixed format: use Environment.NewLine instead of \n.



Comments
Avoid useless comments such as //strings. We all know these are string instances: "Hello!", "Enter a color\n1 = blue\n2 = red\n3 = Magenta", "Render numbers". Don't comment out code that you don't use, remove it entirely: //string Nums = "";.



Naming conventions
Use pascalCase for variable names: string[] arrays instead of string[] Arrays. But what does arrays mean? Use a meaningful instead: string[] promptMessages for instance.



Using an array or not
There is no reason to wrap the messages in an array. Console.WriteLine(Arrays[1]); is a disaster for readability. Console.WriteLine("Enter a color .."); is much cleaner. On the other hand, string[] color could have been declared as ConsoleColor[] colors. This way, you could have avoided all that repetitive code. You should try to write DRY code.

var colors = new ConsoleColor[] {
    ConsoleColor.Blue, 
    ConsoleColor.Red, 
    ConsoleColor.Magenta
};

// NOTE: this is a trivial parsing, you should perform some validation..
// 0 for Blue, 1 for Red, 2 for Magenta
char userColor = int.Parse(Console.ReadKey().KeyChar.ToString());

Console.ForegroundColor = colors[userColor];
Console.WriteLine("Do you want to continue? y/n");
var nextTask = Console.ReadKey().KeyChar;
Continue = nextTask == 'y';




Console input
Don't read an entire line when you only need a single character: string NextTask = Console.ReadLine(); if (NextTask == "y") { ... You can read a single character: string NextTask = Console.ReadKey().KeyChar;. Unlike ReadLine, ReadKey does not wait for Enter key to be pressed, but immediately returns the pressed key.