Created attachment 355368 [details]
Canvas and Video element with 2 slightly different colours
If you draw on a canvas and use canvas.captureStream the resulting colours in the video are slightly different than the colours on the Canvas. This is also the case a bit in Chrome and Firefox but in Safari it is quite a bit different.
See https://output.jsbin.com/rebesum where a new random colour is drawn every 1 second on both a Canvas and a Video. It's more noticeable with some colours than others.