Washed out colours when converting MOV to WEBM using FFMPEG

Question

I'm trying to convert a simple animation from MOV to WEBM so it can be used as an OBS alert for my Twitch stream.

However, when I convert using FFMPEG, the colour is slightly washed out.

This is what I'm currently using:

ffmpeg -i "file_name.mov" -c:v libvpx-vp9 -lossless 1 -auto-alt-ref 0 "file_name.webm"

I was not expecting the colour to be slightly washed out.

Is there anyway to ensure that the WEBM, once converted from the MOV file does not lose its colour?

Many thanks.