How can I do color grading that changes over time? I just bought a cheap action camera that I plan to use when freediving and my first test shows that the video quality is quite good. The only thing that isn't good enough are the colors.

I started iMovie and managed to get good colors above water and under water but never both at the same time. I realise that I would need to gradually change color as the depth changes and this doesn't seem to be supported in iMovie.

Which software or app, preferably free but not necessarily, can be used to do color grading that changes over time?
DaVinci Resolve seems to be an industry standard software for color grading that exists as a free version. Here is a tutorial on how to use keyframes to animate color grading that worked for me: