else if(clr9[0].Equals(clr9[1]) && clr9[0].Equals(clr9[2]) && clr9[0].Equals(clr9[3]))

else if(clr9[0].Equals(clr9[1].Equals(clr9[2].Equals(clr9[3]))))

if(clr9.Skip(1).All(c => c.Equals(clr9[0])))

if (clr9.Distinct().Skip(1).Any())
{
  //Do something
}

public static bool In<T>(this T val, params T[] options)
{
    return options.Contains(val);
}

else if (clr9[0].In(clr9.Skip(1).ToArray()))

else if (clr9[0].In(clr9[1], clr9[2], clr9[3]))

else if (clr9[0].In(clr9.Skip(1).Take(3).ToArray())