As Jeff mentioned, there is sometimes confusion when people refer to subtitles.
Sometimes, they actually do mean "subtitles" (aka Closed Captioning) which are the words that appear at the bottom of a video that display the dialog, sometimes in a second language. Those subtitles actually have a dedicated track and AV equipment can turn that on or off as desired by the end user. There is no ability to fade or change color or affect any part of subtitles other than the content itself and when it appears.
Other times, as is the case here, the "subtitles" you're looking for are actually titles, and you have free reign over all aspects: font, color, on-screen location, transitions, fades, motion, etc.
While titles and subtitles can perform similar functions, remember that if you're not looking at providing a CC service, you're actually talking about titles. I hope that helps!
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