A high pressure washer, and cement paint, tinted white.
I would use a pressure sprayer/washer to get rid of the old paint then go to a paint store and get their recommendation on a good outdoor paint for your wall.
you can use a paint scraper and berh make a really good cement paint. :)
i have a white cement wall that is starting to peel..my ? is how do i remove old paint and what kind of paint is recommended to paint again in white..ty