The players used are the native browser players. So in that sense, you can't override them in a uniform way. To absolutely replace them, you need to hack your own JS API and basically reproduce what the browsers do already (aka control media playback when buttons are clicked, sliders are dragged and so on). But it's probably easier to check browser-specific ways to override the design of the player(s). See for example this
stackoverflow.com/questions/38764152/styling-native-google-chrome-video-controls for styling the Chrome media player. I assume there's something similar for Firefox as well.
In future releases of AllVideos, I do plan on adding customized players as well, which will allow more design control for sure.
