can you just paint lego bricks pink?

you definitely can, but whether you should is a bit more subjective. some people will paint legos to make custom minifigs and the like. personally, i'm not a fan of the end result- since lego bricks tend to have such a uniform texture, any variance tends to stand out that much more and it ends up looking a bit cheap, at least from all the examples i've seen. with bricks especially you also run the risk of very quickly rubbing any paint off due to friction with other bricks, which would be a bit messy. much easier would just be to get sets that have pink bricks already, i just dont have a bunch in my collection because, well, growing up lego spaceships and castles didn't have an abundance of pink bricks :Þ