Highlight.m

- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer willSpeakRangeOfSpeechString:(NSRange)characterRange utterance:(AVSpeechUtterance *)utterance
{
    // Highlight the portion of text that will be spoken.
    NSMutableAttributedString *aString = [[NSMutableAttributedString alloc] initWithString:_textLabel.text];
    [aString addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:characterRange];
    _textLabel.attributedText = aString;
    
}