@ Jacen Solo: It was this thing that you could use to calibrate your TV to optimal tint and colour through the Bungie AV Calibration tool in the Halo 3: LE bonus disc. Basically if you bought anything on the Bungie store earlier you could have it shipped with your order for free. It's a thin plastic blue film that you look through to match up colours and stuff.
Sorry for the Twitter reply, I forgot to quote your line
[Edited on 08.18.2010 3:32 PM PDT]