Rwanda's previous flag was a red-yellow-green tricolour with a large black letter "R" (to distinguish it from the otherwise identical Flag of Guinea). Derived from the flag of Ethiopia, the colours green, yellow, and red represented peace; the nation's hope for its development; and the people. The colours were associated with Pan-African colours. The flag was changed because it became associated with the brutality of the 1994 genocide.

The present flag has four colours: blue, green, and two forms of yellow (standard yellow for the middle band and what the Pantone system calls "sun yellow" for the sun). The blue band represents happiness and peace, the yellow band symbolizes economic development, and the green band symbolizes the hope of prosperity. The sun represents enlightenment.

The new flag represents national unity, respect for work, heroism, and confidence in the future. It was adopted to avoid connotations to the 1994 genocide. The flag was designed by Alphonse Kirimobenecyo.

When hung vertically, the flag should be displayed as the horizontal version rotated clockwise 90 degrees.

More Info: en.wikipedia.org