Hello Wotto, I was attracted to your post by the sensational title, and couldn't help but reply.
I have no idea how much paint you will need.
Actually, I sort of do - I used spray cans prepared by my brother for my JP. I didn't keep perfect track, but I am pretty sure I bought six and used four for the reds, and two for the blacks with some left over. However, the colour depth is much greater than the original.