The flag of Papua New Guinea has an aspect ratio of 3:4. It is divided diagonally from the top hoist-side corner to the bottom fly-side corner, creating two triangles. The upper triangle is red (#FF0000) and features a yellow (#FFD700) five-pointed star. The lower triangle is black (#000000) and displays a yellow-bordered white silhouette of the Raggiana Bird-of-paradise.

As for geometric properties and measurements, the flag can be described as follows:

1. The diagonal dividing line creates two right-angled triangles with angles of 45°, 45°, and 90°.
2. The five-pointed star is equidistant from the edges of the red triangle and centered within it.
3. The Raggiana Bird-of-paradise silhouette is also centered within the black triangle, with the yellow border being of uniform thickness around the bird.

Please note that these descriptions are based on the standard design of the flag; actual measurements may vary depending on specific reproductions.