C#: Remove duplicate values from dictionary?

How can I create a dictionary with no duplicate values from a dictionary that may have duplicate values?

IDictionary<string, string> myDict = new Dictionary<string, string>();

myDict.Add("1", "blue");
myDict.Add("2", "blue");
myDict.Add("3", "red");
myDict.Add("4", "green");


uniqueValueDict = myDict.???

Edit:

-I don't care which key is kept. - Is there something using Distinct() operation?