Hello. I'm a new DIY-er. I have 3 fluorescent lights in my basement. I just installed new ballasts in the first two and the lights work fine. I am having trouble with the third light's wiring. I removed the old ballast without paying much attention because I was able to wire the first two lights without any problem. I connected the new ballast just like I did with the other two lights. When I went to connect the ballast's black and white power lines to the fixture lines, I realized there is a red wire, which I assume is for the switch. I have attached pictures of how I have it wired right now.

The switch controls two lights. The way I have it wired now, the other light turns on when the switch is flipped. However, this light has the bulb flicker and then not turn on. If anyone can tell what I'm doing wrong from looking at the pictures, I'd appreciate any help! Thanks!

Can anyone help with this?

I do not see a problem with how it is connected in the photo, however, I do not know what the red wire is for, I assume you know.

Is the red wire from the switch? Then what is the black for?