I just thought of this, the neon day geckos you are considering aren't the diminutive Lygodactylus williamsi or any other geckos of the genus of Lygodactylus? They are sometimes called day geckos and williamsi is quite colorful, a screaming blue color. With the pet industry's inclination to make up new names I am thinking that this species could be also called a neon day gecko.
If L. williamsi is your neon day gecko, I would say in no way should you mix the two. All Lygodactylus geckos are wild caught from Africa, so they will be carriers of African pathogens to which the dart frogs have no immunity.