Best answer by Maryam
It looks like your query pertains to subtitles in Coursera's video lectures in general (although you've posted it in this forum).
You can turn subtitles on/off and select a particular language. But, no, there is no option for customizing the look and feel of them. Please feel free to start a new thread in the Coursera Ideas & Suggestions forum. Make sure you'll provide some more information on the improvements you have in mind: Read this first: Best Practices When Making a Feature Request
All the best.