HTML/CSS Hero page Animation HELP

Hi, I’m very new to all of this. I’m currently building a hero page for my website, and I’d like this to be the background. I’m looking to be able to toggle this blend mode animation/transition at whatever point the ‘static’ video is at, all on the click of a button. The idea would be to reveal content (text, etc.) whenever the video goes fully black and white. I’d like to preferably do this with an MP4, but a GIF would work as well. Any advice or guidance would be much appreciated! Thank you!