The flag of Guinea-Bissau features three vertical stripes and a red star on a black background. The aspect ratio is 1:2.

Colors:

• Left stripe: green (Pantone 361 C, HEX #1EB53A)
• Middle stripe: yellow (Pantone 116 C, HEX #FFCD00)
• Right stripe: blue (Pantone 286 C, HEX #0072CE)
• Star field: black (Pantone Black C, HEX #000000)
• Star: red (Pantone 485 C, HEX #DA291C)

Geometric properties and measurements:

• The vertical stripes are equal in width and occupy one-third of the flag's width each.
• The black square with the red star is located on the upper hoist side and spans half the flag's height and occupies one-third of its width.
• The red star has five points, is centered within the black square, and has a diameter equal to one-third of the height of the flag.

No other specific measurements or geometric properties are provided.