Reprime all walls and the ceiling with a 100% acrylic stain blocking primer. An interior or exterior type of paint primer is the best choice. I recommend Zinsser 123 primer; for deep or true colors use the deep tone base tinted to approximate your final paint color.
For the finish coats use a 100% acrylic exterior semi-gloss paint. This will be more resistant to water vapor. To further reduce the steam within your bathroom install and use a ventilation fan.