You can change the font, size, shadow, and background color of subtitles and closed captions.
To change the appearance of subtitles and closed captions:
From a web browser, go to your Netflix Account page.
From Profile & Parental Controls, select a profile.
Select Change for Subtitle appearance.
Choose your subtitle appearance settings.
Open the Netflix app on your device.
For instructions on how to change the subtitle and closed caption appearance on Apple TV, iPhone, iPad, or iPod touch, go to Apple Support.