I couldnt figure out what movie you're trying to do, but a lot of movies dont have the extra detail to warrant 4k. For example, i compared shang chi 4k vs 1080p and i couldnt find additional detail anywhere. A digital download is designed for streaming so any additional detail would most certainly be crushed anyway. Upscaling with something like topaz would potentially give a perception of an improvement, but i personally would use that sparingly as its not authentic.
with regards to colour data, 4k releases are generally in hdr, so there is additional colour data but i am not sure how workable that is.