Eventually one color will completely take over the screen. Which one is completely random. Sometimes it can be done in 5 minutes, sometimes it takes hours.
This program exists for UNIX (using MIT SHM extension of the X server) and for Win32 (using Direct Draw).
Initialization, the blues are going down, the reds are coming up.
Collision! They will mostly stop each other now.
Equilibrium. They will struggle a lot here to break through each others defenses.
Red breaks through!
Because red has weakened its defense by leaking through, it gives blue a chance to break through.
Smaller collision, more breakthrough.