In the same way everything is. It's friendly and bright, and yes those are valid criteria.
Edit: I'm being downvoted, but how else do you advertise towards children? If your vape ad looks like the toy aisle then who is it marketing towards? Toys are marketed towards children by being bright, colorful, and friendly looking. They aren't marketing towards the parents with that, right? If it's valid to say that about toys then it must be valid about other products as well. Disagree? Give a counter argument. Can't come up with one? Why do you disagree then?
Having bright colors makes it more appealing to everyone but is an especially effective marketing tactic for children. Of course it doesn't only appeal to children, but it's a provably effective way to get children's attention.
I'm not about to watch some ads to win an argument on the internet. Here's this though, which I added into an edit above but you may have not seen that.
This video is unbearable to watch. It's even worse than the DARE crap in the 80's. If this is your proof that there are ads directed at kids I'm sorry but it ain't it.
Did you even watch it? I don't remember, but I don't think it's anti-vape or anything. It just discusses how they've forgotten why anti-smoking ads worked. It's largely a media analysis channel.
Rewatching it, it literally uses DARE as an example that doesn't work. It also talks about smoking weed in a non-negative stance.
It's literally just about effective messaging, politics, and history, not about the product. I'd recommend getting past five seconds. There's some negative statements about smoking, but the only negative statements about vaping is that nicotine addiction is on the rise now.