The Cloud guitar first appeared in 1984 during the Purple Rain era. In the film, Apollonia gave the guitar to Prince as a present 
(he then gave her one of his earrings - fair swap I think!). The guitar was actually made by David Rusan of Knut Koupee Music 
in Minneapolis. The original design of the guitar hasn't really changed over the years, except for a few cosmetic details. 

The Cloud is made totally from maple and is built with the neck going right through the body. The side 'wings' which make up 
the body are then glued on. The neck of the guitar features a 24.75" scale length (the same as is used on Gibson guitars such 
as the Les Paul). It has 22 medium/jumbo frets fitted to a 12" radius fretboard. The neck is angled back slightly to compensate
for the height of the Schaller bridge/tailpiece. 

The 'nut' on the guitar (the part that the strings pass over nearest the head) is made from brass. This gives a nice 'bright' sound
to the guitar and also adds sustain. The machine heads are Schaller M6's and are gold plated to match the rest of the guitars hardware.

The most striking features of this guitar are the carved 'scrolls' which appear on the lower part of the body, the head and most notably, 
the upper horn. This 'classical' styling seems to blend flawlessly with the modern electronics and the exquisite paintwork. 
As you will already know, Cloud guitars are painted all over,  including the fretboard. The one exception to this rule appeared in 1985/86. 
It was a black Cloud with a natural maple fretboard. This guitar hasn't been seen in public since and may have been re-painted. 
Another black cloud appeared in the Batdance video in 1989 - perhaps that was the same guitar?

The pickups on Cloud guitars are American made EMG units - an 81 humbucker at the bridge and an SA single coil at the neck. 
These are active pickups (noise-free and capable of retaining their clarity at any volume setting) and run from a single 9v battery. 
The signal from the pickups is routed through a 3 way switch, then to a single volume control (25k-ohm) and a tone control (25k-ohm). 
The output socket is a 1/4" gold plated jack. The control knobs on the original clouds were black plastic with a white marker on top and 
are described as 'mini JB' knobs (JB standing for Jazz Bass). The guitar from the Rave DVD has gold plated 'dome' control knobs, as do the 
Shecter copies (see below).

The hardware on Cloud guitars is mainly Schaller - The bridge, Machines & humbucker surround are all made by the world-renowned German company. 
The strap locks that Prince uses are made by Dunlop.

Cloud guitars have been made in various colours over the years. These are listed below, together with the year in which they first appeared.

White - 1984 - Purple Rain
Black (Maple fretboard) - 1986 - Parade
Peach - 1987 - Sign 'O' The Times
Blue - 1988 - Lovesexy
Black (Painted fretboard) - 1989 - Batman
Yellow - 1991 - Diamonds & Pearls
Blue - 1993 - Symbol/Act II

The blue guitar is still being used today and can be seen on the Rave video/DVD.

In the early to mid 90's, when the NPG shops were open in Minneapolis & London, you could buy a genuine Cloud guitar. I remember seeing one in the London shop for £3000. These guitars are still around today but I should imagine that the owners are very keen to keep hold of them as they are very sought after. More recently, Paisley Park commissioned American guitar company Shecter to make a number of copies of the Cloud guitars. These were made in white & blue and are being sold on the US leg of the Hit & Run tour. $1000 cash would get you one of these guitars which, although not perfect copies, are still very well made instruments. They feature Seymour Duncan designed pickups and  Schaller look-alike hardware. The most disappointing feature of the Shecter guitars is that the shape of the head is considerably different to that of the original. This is a real shame because the guitar's body is perfectly shaped. These guitars are currently back on sale at www.npgmusicclub.com for $1500