Tokyo Tower is responsible for much of the Terrestrial Digital transmissions in the greater Kanto (region around Tokyo) area. It will be broadcasting at "full power" from December 1st, so to commemorate, the Association for Promotion of Digital Broadcasting pulled a few strings, and the tower will be illuminated with blue lights for the night of December 1st.

Tokyo Tower, which sends terrestrial digital broadcast waves to the Kanto area, will begin sending at full power output (rated output 10kW) from December 1st. To commemorate the event, o­n just December 1st, the top portion of the tower will light up in blue.

This is the second time the tower will light up in blue, the first time being during the 2002 FIFA World Cup. The tower will light up from 6:50PM to 11:00PM, and it will also be broadcast o­n TV.

Also, from 5PM to 11PM o­n November 21st, and from 6PM to 11PM o­n November 22nd to December 1st, the characters "Terrestrial Digi" will be illuminated o­n the glass of the viewing platform. It will be displayed in the direction of Odaiba, and also in the direction of Roppongi.

Inspired by:
http://www.watch.impress.co.jp/av/docs/20051128/ttower.htm

Information from Tokyo Tower:
http://www.tokyotower.co.jp/cgi-bin/2005/renewal/reg.cgi?mode=2&no=64

Information from Kanto Bureau of Telecommunications:
http://www.kanto-bt.go.jp/if/press/p17/p1711/p171118.html

Information from Association for Promotion of Digital Broadcasting:
http://www.d-pa.org/information/info_051122.html