What is best paint to paint treated wood?

I have treated wood for a wider handrail for my handicap ramp. It's painted white because it helps a friend that can only see shadows (his words). His wife had the handrail on their ramp made with a white plastic material. She saw how my rail helped her husband.
I paint it each year but over the Wisconsin winters it chips and needs repainted. My friend is a disabled Veteran with only one eye from his war time injuries so I don't want to just stain it same colors as deck and ramp.
Thank you for any help
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