What steps are there for painting over red paint?
If it's on a house: 1) use a primer, something thick and trustworthy, to cover over every inch of the house - white is a great color to start with as anything can be used on top.
2) After the primer has dried for a full two days, then you want to paint the house the color you're after. Use whatever color you decide, if you're not painting by hand brush & roller, it'll probably take two coats to get the high gloss, professional look that comes from hand brushing or rolling.
Remember drop clothes everywhere, and tape / cover what you can as it's a pain to use a razor blade to go back & touch up windows, etc. While you're you're doing the painting also see if there is any silicon caulking you can fix as that's a good time to get it done as you can paint over it when you're finished.
Powerwash the area you're going to paint if this is an outdoor painting project, and remember, drop cloths everywhere when you start painting to avoid ruining your garden.
Then, apply a flat color primer, either white OR close to white. Then review the first coat to see if you missed any spots, OR if the white primer has a red sheen to it, if it does, then apply a second coat of primer.
After that, then paint the area the new color you're going for.