If you get a bunch of driftwood or rocks jutting out of The water you could get away with these geckos. However other issues to consider. Only male Williamsi are blue. But even then they are only “electric” blue if their husbandry requirements are well met. Which is challenging to pull off while also keeping the dart frogs happy. They want a basking area, uvb, and less humidity than darts. It’s far more likely they will just be grayish/green geckos that aren’t that fancy looking when sharing a tank with darts.
Not saying you can’t pull it off. But if you are going for cool looking, klemmeri are probably a safer bet.