Change the background color of the console with the help of enum
As has been mentioned using a Dictionary&lt;RanngDe,Color&gt; will make your code much simpler:

public enum RanngDe
{
    Blue = 0,
    Green = 1,
    Yellow = 3
}
static Dictionary&lt;RanngDe, ConsoleColor&gt; colors = new Dictionary&lt;RanngDe, ConsoleColor&gt;()
{
    {RanngDe.Blue,ConsoleColor.Blue },
    {RanngDe.Green,ConsoleColor.Green },
    {RanngDe.Yellow,ConsoleColor.Yellow }
};
public static void SetColor(RanngDe R)
{
    Console.BackgroundColor = colors[R];
}


Depending on your implementation you might be able to do away with the method completely and just use the assignment.

I came up with another approach.  If you change the values of Ranngde to be the same as the ConsoleColor enum, you can cast the Ranngde value to ConsoleColor:

public enum RanngDe
{
    Blue = ConsoleColor.Blue,
    Green = ConsoleColor.Green,
    Yellow = ConsoleColor.Yellow
}
public static void SetColor(RanngDe R)
{
    Console.BackgroundColor = (ConsoleColor)R;
}