Flooring Tile - painting over tile (plastic)

Hello, I have a question about painting tile.My bathroom is old and has plastic 4x4tile on the walls .It is trimmed on top with 4x2 black tile.There is no grout,as it is plastic.It is a shiny finish and in pretty good shape.I want to paint over it, and I am not sure what sort of surface prep I would need to use,Or what type of paint to use.The pink color is nauseating.I think it is from the early seventy's.I am not yet in the position to remodel financially.Any suggestions? Thank you !:)

There is a brush on prep stuff called paint sizing(Ithink its called) but just ask for it by saying "whats the stuff I use to paint on before putting on the true color simular to eg; putting latex over oil paint". It's at Ace hardware.