Switch to 709/Partial instead of Full. Full is only if you have a complete end-to-end Full RGB workflow. Chances are good this may be causing your color issues.
Switch to the Quality preset, instead of Max Quality. MQ uses CUDA cores, which can cause issues.
Turn off Psycho-Visual Tuning as well, same issue as MQ.
Don't downscale. Downscaling will incur a quality loss. Hold off on downscaling until your final edit, to preserve as much quality through the entire process as possible.
NEVER record directly to MP4. If you are recording multitrack audio, use MKV. If you only need one audio track, FLV will work fine. You can remux the recording to MP4 later from OBS' File menu, Remux Recordings.
If any issue occurs when recording to mp4, the entire recording will be rendered corrupted and 100% unrecoverable. Digital garbage. Also, many major video editors (Premiere, Vegas) have issues with OBS direct-record MP4s.
Beyond that, we can only speak for the videos that OBS provides, not your post-editing videos. Those go through another rendering and encoding step that we cannot assist with, and any number of things can go very wrong there.
