I have a problem. I inserted a video on my website, which has a blue background. I picked the color with the tool dedicated, to put the background color with the same color. On my laptop and on all retinas screens it seems to work (screen1) But on some other one, people can see a square like its not the good color (screen2). Any idea to fix this ?
As far as my understanding you are using a compressed video file. Same as jpg.
To achieve compression it reduces colours and produces patterns.
For photos you use png so you guarantee the colour or use transparent.
For video you could sample the colour of the video and change your page to that.
