V4L2 Webcam has weird colours in Motion stream, normal on VLC

I've set up a webcam stream with Motion to use with Octoprint on my Raspberry Pi 4 (Raspbian 10). With my main webcam (Logitech C270) it works well as expected. I was testing to see if I could use a quite old webcam (Sunplus Flexcam 100 according to lsusb) I just found. I've managed to make it work, through VLC I can see the video feed just fine: (my red jumper and a green plastic object as color reference) However, when I start Motion, the image I see on the stream has the colours distorted (kind of looks like green and red are interchanged): I've tried changing the palette and hue config options, but nothing changes. I've also tried using the v4l2 prefix, as in v4l2:///dev/video0 in the videodevice config option, but it does not recognize it as valid. Any ideas as to what might be happening? Thanks in advance