I have been thinking about getting a couple of tritium keychains. I'd like one to put on my dog's collar so I can see her in the dark. Just tonight I tripped over her when she was sleeping in a dark hallway, plus she likes to wander around the yard in the dark. First question: Is tritium safe to put on my dog's collar? Second question: Where is the best place to by it from cheaply? Third question: I assume green and yello are the brightest colors, right? Anything else I should know about tritium?