Generally, recorded video is usually compressed, which can cause some color loss compared to the original screen.
If you want to record in lossless mode, you can use the Lagarith Lossless Video external codec.
You can download it from the following address.
http://lags.leetcode.net/codec.html
After downloading, install it as shown below.

If oCam is already running, restart it. Then in the oCam main window, click Codec - External Codec, check the Use External Codec box,
and select Lagarith Lossless Video from the list.
After selecting it, click Settings. The settings window opens as shown below. Usually you can leave it as is, but you can adjust it according to your environment.

Note that this codec produces visually lossless video, but the resulting files are very large and decoding takes a long time, which may cause playback stuttering.
Therefore, this codec is generally better suited for editing purposes.