What is the best way to cover dark red paint?

Coat it with "Stain Killer" first then paint it with any good paint.

Stain Killer is available wherever paint is sold.

Paint over it with primer and then paint it with a new color. There may be a primer that specifically covers dark paint. Ask at the paint store or big box paint department.

We had a dark salmon pink to cover when we moved into our house...plus it was a high gloss paint. We sanded the wall lightly and then applied two coats of primer and then painted the wall with light blue...can't even tell it was ever that other ghastly color.

Get a good high quality primer to paint with first, then go over the primer with whatever color you've chosen.

I'd expect multiple coats of a high quality paint.

A good quality primer let dry overnight then paint whatever color you wish.

use "killz primer" it will cover that up in about 1 to 2 coats maximum

all the above are good choices