Yes you can, you just have to specific the pixel format. To get the whole list of the format:
ffmpeg -pix_fmts | grep -i pixel_format_name
For example if you want to save the 1st video track of an mp4 file as a yuv420p (p means planar) file:
ffmpeg -i video.mp4 -c:v rawvideo -pix_fmt yuv420p out.yuv