def isAdditivePrimaryColor(color):
    """
    return True if color is a string equal to "red", "green" or "blue", otherwise False
    >>> isAdditivePrimaryColor("blue")
    True
    >>> isAdditivePrimaryColor("black")
    False
    >>> isAdditivePrimaryColor(42)
    False
    >>>
    """
    
    return ( (color == "red" ) or (color == "green" ) or (color == "blue") )