Supply correct pixel format & parameters from gphoto2 feeding into ffmpeg using v4l2loopback

I have Nikon D3300 camera and want to feed video output into my computer as part of live streaming with OBS.

I successfully installed v4l2loopback as well as gphoto2 on my Ubuntu 18.04. I already had ffmpeg installed. (Their all version information can be found at the bottom)

Then I execute the command gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video2. I tested to see video output via guvcview and OBS. It shows video output properly but with one issue. It looks greenish like this (captured from OBS).

I also asked in v4l2loopback on github and developer pin-points that the problem is with the parameters feeding the program i.e. gphoto2 (or need some adjustment of parameters in ffmpeg too or not I'm not sure).

So do you know whether I use the right parameters? or else what's the right ones to solve this greenish video output.