I too take a long time to fall asleep. My best trick that works most often is to watch a movie: not something I've never seen, because it keeps my interest. A movie that I know and love because then my mind listens to the dialogue, but doesn't have to pay close attention so I can sort of stop the rampage of thoughts and just fall asleep. It doesn't always work. I don't actually like going to bed/sleep, but I do love to sleep in. I'm a major night owl. Actually though, sometimes I feel trapped when I am sleeping in. Like I want to get up but I just can't, I must keep sleeping/dozing.
As mentioned earlier, I also need noise to sleep, like a fan or a humidifier. And yes, I dream vivid, colorful dreams, and I can usually remember them for a little while, but I forget if I don't write them down or tell someone about them. I don't always dream though, and I sort of don't like to, because sometimes my subconscious brings up things that have happened or are bugging me that I don't want to think about or things that might happen in the future that I also don't want to think about.
I hadn't attributed these things entirely to Ni, I'm very interested and very glad that you posted this question!