Okay, so I played the movie back on libTAS 1.4.6 using the latest version of the game (last updated 61 days ago as of this writing) to look at the colours on my Kubuntu VM on VMware Workstation 17.5.2. For transparency's sake, I did not mess with the colour settings in the VM itself, and is using the stock configuration in that regard.
The final result: On both software and hardware rendering, I got the same colours as on the latter half.
Hardware renderer
Software renderer
So to me, these seem like the actual intended colours.
As for the movie not going back to the title screen, I believe this is intended from my understanding. The
rules state that suitable endpoints are either a definitive ending, such as a credits sequence, a kill screen, or in the case of there being no clear ending, either all unique content being exhausted and completed, hardest in-game difficulty loop being completed or maxing out the score. There's an additional bullet point for ending the movie at some logical or artistic stopping point in order to make it more entertaining, but that doesn't apply here, as it's a Standard publication.