It's a special paint that you paint over plastic flowers.
Here are some ideas for how to paint porcelain: https://blog.hobbycraft.co.uk/15-ways-to-paint-porcelain/
Hi Patrice, are you talking about Petal Porcelain? I believe it was made by Plaid. I have seen people make the flowers and arrange them in a vase or attach them to candle holders, vases, lamps and mirrors. I saw this on eBay...books for ideas. https://www.ebay.com/i/401599281500?chn=ps Maybe it'll have something of interest. Hope it helps!
I put "porcelain pretty paint" in the search box and a good number of projects came up called "pretty paint". I did not realize it was a type of paint until you asked. Here is one I found for you, I hope it is what you meant. You might want to do the same in the search box and find one that better suits what you need. Here is the one I chose: https://www.hometalk.com/9562350/how-to-paint-on-mugs