South Africa
I don't know what the design means or what the colours symbolizes, but here's what Wikipedia says:
The current flag of the Republic of South Africa was adopted on April 27, 1994, after the first free elections and the end of apartheid. A new national flag was adopted to represent the new democratic government of South Africa that represented all South Africans.
None of the flag designs submitted by the public was supported by the committee charged to select the final design. An interim flag was designed by State Herald Frederick G. Brownell for the April 27 elections, the nation's first fully inclusive elections, and for Nelson Mandela's May 10 inauguration. The flag was so well received that the interim version was made the final, national flag in the South African Constitution. Given the troubled historical context, it is remarkable that a consensual replacement for the former national flags was found. The new flag is seen as an enduring symbol of the modern South African state.