First of all, you should consider halting your search for rainbows. If you are not one of those that is prone to seeing them, then you should just accept it and watch happily. If you force the issue and discover them, you will probably see them from that point on.
Now, with the warning aside, there are particular scenarios where rainbows can be more prevalent:
1. Black and white video, especially the credits
2. Turning the lights completely off
3. Being overtired seems to draw them out
4. Fast action on the screen
5. Finally, the standard quick jerk of your head to either side can draw them out.
Rainbows are nothing more than your perception of what is already there for all to see. You have to remember that DLP involve rotating color wheels and mirrors. The positive news is that the increases in color wheel speed have helped to reduce the prevalance of the rainbow effect....just as the fill rate on LCDs has steadily increased.
Finally, all must understand that people's perception and frustration w/ rainbows tends to subside w/ time. First of all, you tend to eventually forget about them as you focus on the material. Also, you seem to get used to them where you tend not to see them.....Yes, it sounds hokey, but you do get over it. At the time I bought my DLP PJ, I saw rainbows, but I easily traded that for the amazing picture quality, contrast, etc. Now, I rarely notice them and pay little attention to them when I do see them.
