you don't understand the process of compression
you will cumulate color errors all the time
first step - video was lossy compressed by camera (a lot of lossy steps here btw)
second step - video was lossy compressed by youtube
third step - video was lossy compressed by video player when saving as JPEG
fourth step - video was lossy compressed by image editor when cropping and saving as JPEG
fifth step (optional) - video was lossy compressed by cloudflare (if polish feature was enabled)
the point is to keep the original pixels as much as possible