Misc: What colour on black produces the most visible combination?

Questions

08 February 1971 South Vietnamese troops invade ---------- ?

09 February 1971 Quake in ---------- Valley kills 65 & causes over $1/2 billion damage ?

10 February 1971 Royal Albert Hall bans scheduled concert featuring Frank ---------- ?

13 February 1971 12,000 South Vietnamese troops cross into ---------- ?

14 February 1971 Richard ---------- installs secret taping system in White House ?