def validate_array(ary)
      correct_size = ary.size.equal?(3)
      correct_vals = ary.all?{ |val| val.is_a?(Integer) && val.between?(0, 255) }
      return true if correct_size && correct_vals
      raise ArgumentError,
            %|invalid value for PryTheme::RGB#validate_array(): "#{ ary }"|
    end
def validate_array(ary)
      correct_size = ary.size.equal?(3)
      correct_vals = ary.all?{ |val| val.is_a?(Integer) && val.between?(0, 255) }
      return true if correct_size && correct_vals
      raise ArgumentError,
            %|invalid value for PryTheme::RGB#validate_array(): "#{ ary }"|
    end
Checks whether the +ary+ has correct number of elements and these elements
 are valid RGB numbers.

 @param [Array<Integer>] ary
 @raise [ArgumentError] if the +ary+ is invalid
 @return [void]