Ffmpeg Scrolling end credits with transparend background from png

Question

Trying to create an end credit video from the following large pixel png file (with transparent background). Creating the scrolling video works but the background is not transparent. What is wrong with my command?

ffmpeg -f lavfi -i color=s=1920x1080 -loop 1 -t 0.08 -i "credits.png" -filter_complex "[1:v]scale=1920:-2,setpts=if(eq(N\,0)\,0\,1+1/0.02/TB),fps=60[fg]; [0:v][fg]overlay=y=-'t*h*0.02':eof_action=endall[v]" -map "[v]" -pix_fmt yuva420p -vcodec prores_ks credits.mov

The picture I am using

Answer 1

thanks to @Kesh using colorkey worked with the following command

ffmpeg -f lavfi -i color=red:s=1920x1080,colorkey=red,format=rgba -loop 1 -t 0.08 -i "credits.png" -filter_complex "[1:v]scale=1920:-2,setpts=if(eq(N\,0)\,0\,1+1/0.02/TB),fps=60[fg]; [0:v][fg]overlay=y=-'t*h*0.02':eof_action=endall[v]" -map "[v]" -pix_fmt yuva444p10le -vcodec prores_ks credits.mov