You should try
this light. Stands out against the background quite nicely, unless you're riding through Vegas. In which case, I doubt that there's anything you could run that'd stand out, day or night.
For what it's worth, I see numerous cyclists running flashers during the day, and they do stand out, to my eyes. Flashing lights don't get lost in the background any more than dayglo clothing does, provided it's a decent light. Most modern LED bike lights are bright enough to be seen from distances important to a cyclist, even during the day. Motorcycle headlights obviously need to be much stronger, seeing how fast they can travel. But lights that're less strong than automotive lights are still visible.