ffmpeg - get green overlay instead of red when using multiply? multiply should result in a darker image according to this website. However every multiply options with input that I'm using resulted in darker green videos instead of layering it with colour that I use for layering.

Many people refer that as format issue and resolved by using format=rgba options, however in my case there I'm still stuck.

FFMPEG command :

ffmpeg -i red.jpg -i car.mp4 -y -filter_complex [0][1]scale2ref[a][b];[a]setdar=1/1[c];[b]setdar=1/1[d];[c][d]blend=all_mode=multiply:all_opacity=1[out];[out]eq=contrast=2:brightness=0.5[ckv] -map [ckv] output.mp4


with format=rgba

ffmpeg -i red.jpg -i car.mp4 -y -filter_complex [0][1]scale2ref[a][b];[a]setdar=1/1[c];[b]setdar=1/1,format=rgba[d];[c][d]blend=all_mode=multiply:all_opacity=1[out];[out]eq=contrast=2:brightness=0.5[ckv] -map [ckv] output.mp4


assets in case someone want to try it.
- Images
- Videos

FFMPEG version 4.1
Your command is wrong, if you enable debug log messages, you would notice that yuv formats are still being used.
You need to put format=rgba filter to all inputs and outputs of blend filter to make it work as you want.