Awwr, what a cute idea! I'd assume any paint that's safe for kids should be safe for your Dragon, provided he/she does not ingest any. I'd be careful to use it only on the paw and wash it off immediately after, so they can't lick it or anything like that (since they lick things in their environment to learn more about it). They're much smaller than us and therefore need far less of something to be poisoned by it, in comparison to us Humans. But overall, this should be a relatively safe activity if done right. Just have a moist facewasher nearby to clean the paw afterwards then immediately remove it from their environment once done.
I personally think it's safe if done right, but others here might think differently. It's their right to express that viewpoint.