Imps! graphic subtitles
YouTube has provision for uploading CC ClosedCaptions in formats including SubRip.
Miyu is a free Mac program for creating these captions and Miyu provides for a choice of fonts, colours and effects. These can be rendered to a number of formats including QuickTime movies but are not included in the SubRip file uploaded to YouTube. YouTube has the default white text on a black background shown above.