Hi, I will look into the dual replay sync issues. Could you describe the image size and frame rate of each camera, I'll emulate the same to investigate. They are both 720 x 540 @520 fps?
For color, when you are using a Bayer stream format (telltale is the little grid pattern on top of the black and white frames) you have two options:
1. Debayering on the fly: in the camera parameters check the "Enable software demosaicing". This will add a little overhead so if it makes things even worse regarding dropped frames try the second option.
2. Debayering during playback: in Preferences > Capture > General > Record uncompressed video. This ensures the raw frames are saved as-is to the file which is necessary for this to work as we need pixel perfect precision to retain the Bayer grid data all the way. Then when loading videos in the player: Image > Demosaicing and selecting the Bayer format. Note that these raw uncompressed files are not supported by many media players and those that support it might not have the option to rebuild color during playback.
For the first approach I realize that since you are using "retroactive" mode there could be a third way where the debayering is done at the end during the saving process. This is not implemented at the moment.
(color cameras always start with these patterned B&W images but they do the debayering on the hardware, which is not necessarily faster and requires 3 times the bandwidth, that's why the only way to get the top frame rate advertised by the vendor is to go with the bayer format. Also don't bother with the higher bit depth formats like 10 bit or 12 bit, Kinovea doesn't use them, they get converted the same and just eat bandwidth for no additional benefit).
