I think is fine for any child to play around with their parents' make-up and play dress up at any age. I do not think, however, any child should be bought make-up, or be dressed in make-up to go out in until they are at least 15.
I would never prevent my child girl/boy from playing with make-up. Makeup for kids is about exploring, playing, creativity, experimentation. I use to love putting on my Mum's red lippy and heels...and I still love putting on makeup. 3 or 4 yrs and up is fine. As long as they are past the stage of wanting to eat it. :)
Even without trying, most of the people end up ingesting lipstick. Most of them contain lead. Lead is a neurotoxin and can be dangerous even at small doses.
I would keep my kids away from atleast lipstick. Other things, they can play with it but then not too much.