RAINBOW question

[Chibi_Venus]

I have a couple of questions on this beautiful piece.

= I understand that she thanks all RAINBOW lovers. Is that because some people gave her ideas for the song? (<-- kind of a, "I can't remember" question.)
= Is the song for RAINBOW lovers? For example, "Who..." she's singing to her grandmother and "teddy bear" she's singing to her father. Or is this just another song sung just using the word "you" (no one in particular) like most artists do.
= Any reason it's called RAINBOW? My guess is that... well, it's hard for me to explain. Or should I just look at the lyrics again?

Sorry if I sound like an annoying fan who just wants a couple of answers.