Rather hard to properly diagnose this one off such a short description, but...
1/ Bulb OK, not over hours or otherwise damaged?
2/ Is it constant for all images, just a general coloured haze, not a strange "shadow", "ghost" or "fringe" that alters depending on what you display?
3/ Lens nice and clean?
4/ Surface you're projecting it onto also clean and at least nominally white?
5/ Input cables all fine at both ends and work correctly with other output devices (TV and/or computer monitor)?
6/ Haze still in place with different cables and input devices?
7/ Does the projector regularly show the same static image for extended periods?
The VT460s were buggers for suffering from internal LCD and filter glass issues if allowed to overheat, and with image burn-in, especially if fitted with unusual lenses (e.g. extreme short-throw); I've had to do internal cut-and-swap surgery on a few of them before, with donor image elements from projectors that died due to other problems. I can't say the one VT470 has shown any sign of similar, but the two VT480s are worse if anything. So it's entirely possible that we just got the one good VT470 out of the whole production run. As intimated by the above, it could be anything out of a failing bulb, dirty lens (or internal image element) glass, image burn-in, LCD/filter damage from overheating (and mind that being turned on showing a "blank" screen for ages can cause a similar effect, as all of the bulb's 200 watts of light energy is then being completely absorbed by three thumbnail-sized pieces of liquid crystal... the bulb doesn't turn off unless the projector is shut down completely!), problems with internal circuitry, dodgy cables, unsuitable projection surfaces, or problems with the devices feeding images to it. It really is a minefield until it can be narrowed down.
on Jan 08, 2014