Is there any information on the Region of Dreams or any such dream related planes in 2e books or on the net?
I have the 3e Manual of the Planes, but the information there isn't detailed enough compared to the info on the other planes in 2e planescape sources.
Any help would be appreciated! 
Also - on the Ethereal plane there's the Wall of Color - if anyone recalls the details on that particular location?
It's the border between the Deep Ethereal and the Border Ethereal. It's a two-dimensional wall of shimmering hues.
Inside, is the Region of Dreams. The Nightmare Lands was the first to make that identification.
Interestingly, based on some PC backgrounds and actions, it's looking like the Region of Dream is going to end up playing a very large part in my just-starting PnP Planescape campaign...so I'll probably be fleshing it out quite a bit for my campaign purposes. 
As far as 2E sources, there really aren't any 2E Planescape sources that cover the Region of Dreams in any sort of detail. It's touched on in the Guide to the Ethereal Plane, and features somewhat in the adventure Something Wild, but it was never covered in as much detail as even the woefully ignored Inner Planes, and certainly not nearly as much as any of the Outer Planes. As Rip said, there's the Nightmare Lands boxed set (which was actually a Ravenloft product, but which was explicitly referenced in Something Wild), but even that doesn't have all that much detail on the Region of Dreams itself. It's the most thorough canonical source on rules for how things work in dreams, but it says very little about the Region of Dreams (which I'm pretty sure it never refers to by that name) itself; it's mostly, of course, about the Ravenloft domain of the Nightmare Lands, which is associated with the Region of Dreams but not identical to it.
(On a side note, the Nightmare Lands have featured heavily in a previous DnD campaign I ran...the PCs got drawn into Ravenloft fairly early in the campaign and spent most of the rest of the campaign trying to get out, which they finally accomplished by going to the Nightmare Lands, entering the nightmare of an NPC they knew who was back on the Prime, and then defeating the member of the Nightmare Court in charge of that particular nightmare, thereby waking the dreamer and bringing them back to her location on the Prime...)
So, if dreams are associated with the Ethereal, wouldn't that mean that people on the Astral and Outer Planes can't dream?
I believe dreams funnel through rifts, portals, the prime to the astral and the like. Now wouldn't that be an interesting idea? Finding a dream channel - like a river of color going someplace...
Hm. An interesting possibility. However...Are dreams associated with the Ethereal?
Sure, in 2E it was said that the Region of Dreams was an Ethereal demiplane (or within the Wall of Vaporous Color on the Ethereal Plane). But then, the Plane of Shadow was once thought to be a demiplane in the Ethereal too. And so was the Temporal Energy Plane at first (or whichever of the half-dozen or so other names you want to call it by), though it's since been made clear that can be accessed from planes that don't connect to the Ethereal. Maybe it's just that not much was known about the Region of Dreams, so it was assumed to be a demiplane because, well, that's the first assumption people generally make about unknown planes. So the idea grew that it was associated with the Ethereal, and because of that people usually got there from the Ethereal Plane, which reinforced the idea. But, just as the Plane of Shadow turned out not to be a demiplane at all, maybe neither was the Region of Dreams; people are familiar with means of accessing it from the Ethereal, but it does touch other planes as well...
(Actually, in my campaign, the Region of Dreams touches pretty much every plane; it's one of three planes (Rule of Threes, you know) to do so, the others being the Plane of Time and the Plane of Shadow (which isn't really a Transitive Plane, whatever the Manual of the Planes says...there is a third Transitive Plane, but it is, of course, the Ordial...not that that's likely to come up at all in my current campaign.))
The Astral Plane is actually full of dreams that whistle through the plane with the other thoughtwinds. The difference is that dreams are born in the Ethereal - the Astral is where they go when they're not dreamt any more, where they blow forever through the silver plane among the dying gods.
You could assume that people in the Outer Planes dream, but their dreams are all secondhand, dreams of strangers, dreams of bodies not their own, voyeuristic glimpses into the lives of people still living and long dead.
Personally, I've assumed there is a dreamscape in the Outer Planes, but it's different for each plane; all dreams are influenced by each plane's point of view. The dreamlands of the Wastes are different from the dreamlands of Carceri, which are of course completely different from the dreamlands of Elysium.
i had a dream once 
A good 3e resource would be Dragon #287 which has 4 alternative options for a plane of dreams, where you could pick and choose what you want from there.
Doesn't Eberron have a Region of Dreams? With the Dal'Quor and stuff? Or am I wrong
Yeah, Dal Quor is a region of dreams. You could put quori into any campaign's dreamland.
Any help would be appreciated!
The best source was the Nightmare Lands boxed set.