I just bought a home and the old owners had one of the bedrooms painted this almost navy blue walls. How can I cover this in the basic navajo white without 20 coats?

Thank you

Kilz primer will coat the dark color for a light color to be applied

Agreed, primer does the trick, though you still may have to put on an extra coat

As the others have stated, use a primer.

For primers, like for painting, it is better to put on two thin coats than a single thick coat.

Make sure the primer is a high hide style (Kilz, Behr Enamel Undercoater, etc)

Don't worry if it still looks a little dark after the primer is on, the paint will cover it.

I like Kilz, too.

Primers tend to have too much silicates to really hide. Look at the percent titanium dioxide, TiO2, listed on the label and buy the highest. ( May be Kilz.)