Colors in neovim not shown

Hi all,
I just uploaded my first asciinema cast:
https://asciinema.org/a/zNLcS20lFtzuL0pDkVXPQwfc1

The problem is vim (neovim 0.4.3 to be accurate) is shown somewhat monochrome but it is not. The following screenshot shows the same source file how it has been recorded:

If I download the screencast and replay it locally (with asciinema play 333664.cast) the colors are back to normal, so I suppose the file has been uploaded properly.

Any hints?