People were forcibly being exposed to this blue light emitted by those machines or chairs like what eye doctors use to look close into your eye. After that, people start going zombie-like emo crazy things. One scene I clearly remembered was a girl threading a necklace through slits of skin on her neck going under then over the skin.

Watched it around 2000?

English movie

Saw on TV maybe on an HBO or SHOtime Channel? It was during late night.

Movie was in color.