A recent change (I think) to #YouTube's web UI (at least in dark mode) is that the progress bar is now a gradient from their brand red to deep pink (#ff0033 → #ff2790). I'm all for pink but first I thought my laptop screen was broken and colours faded on the sides, since the video was taking up most of the screen… 😅 but it's normal, yay! Not sure why but… why not.