public IEnumerable<IEnumerable<T>> GetPowerSet<T>(List<T> list)
{
    return from m in Enumerable.Range(0, 1 << list.Count)
                  select
                      from i in Enumerable.Range(0, list.Count)
                      where (m & (1 << i)) != 0
                      select list[i];
}

public void PowerSetofColors()
{
    var colors = new List<KnownColor> { KnownColor.Red, KnownColor.Green,
        KnownColor.Blue, KnownColor.Yellow };

    var result = GetPowerSet(colors);

    Console.Write( string.Join( Environment.NewLine,
        result.Select(subset =>
            string.Join(",", subset.Select(clr => clr.ToString()).ToArray())).ToArray()));
}