Willie Williams was able to plug into the already existing LCD screens used for sporting events. Not all arenas have them.
Here's an posting from @U2.com:
Our friend Tim C. tells me that the lighting has been really different these past couple nights in Chicago, ostensibly for the DVD shoot they're doing. Says Tim:
"Most notable was the use of the electronic LED signs that are usually showing ads for some sort of sponsor during a Bulls game. These signs are located in front of the railing of the 2nd and 3rd Balcony. Willie somehow hooked up into these signs and used them to display horizontal lines of color during points of the show."
He's referring to the image above right, which is something I certainly haven't seen in any photos from the tour so far -- using the main arena lights?? Nice addition. Anyway, Tim continues:
"Secondly, multi-colored LED strobe lights were placed in the stands above almost every single entrance/exit. These were used at certain
points of the show.
I dug through the photos submitted from Monday's show to U2tours.com, and here some shots that show things I've not seen before where lighting is concerned:
http://www.u2tours.com/reviewfiles/2005/18/5463/5463-2.jpg
http://www.u2tours.com/reviewfiles/2005/18/5463/5463-3.jpg
http://www.u2tours.com/reviewfiles/2005/18/5463/5463-5.jpg
http://www.u2tours.com/reviewfiles/2005/18/5467/5467-1.jpg
http://www.u2tours.com/reviewfiles/2005/18/5494/5494-2.jpg
http://www.u2tours.com/reviewfiles/2005/18/5494/5494-3.jpg
That 3rd shot listed above -- where the band's images are on the LED curtains -- what song was that??
One last note: if you noticed that it was super-hot inside the arena, it's because U2 told the United Center to turn off the ventilation system. Why? They didn't want the airflow to interfere with the confetti drop during "Blinding Lights."