Check is user inputs Black, Green or Red. C#

I'm working on a program where I want my user to enter one of the following Colors (Red, Green or Black). But I am stuck.

What I have done so far is this

Console.Write("Color To Bet on: ");
string tempColor = Console.ReadLine();

while (String.IsNullOrWhiteSpace(tempColor))
{
    Console.Write("The color can't be null.");
    tempColor = Console.ReadLine().ToLower();
}

But how can I make sure my users puts in the color I want, I've tried fiddling around with string. Contains method but haven't had any success so far.

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