The flag of the Cayman Islands has a blue field with the Union Jack in the upper hoist-side quadrant and the coat of arms on the fly side. The aspect ratio is 1:2.

Colors:

1. Blue (Pantone 286 C): HEX #003399, RGB(0,51,153)
2. Red (Pantone 186 C): HEX #C8102E, RGB(200,16,46)
3. White: HEX #FFFFFF, RGB(255,255,255)
4. Yellow (Pantone 116 C): HEX #FFCD00, RGB(255,205,0)
5. Green (Pantone 355 C): HEX #009E60, RGB(0,158,96)

Geometric properties and measurements:

1. The Union Jack occupies the upper quarter of the hoist side.
2. The coat of arms is centered on the right half of the flag, taking up approximately half of the flag's length and one-third of its width.

The flag does not have specific measurements for its elements, but they should be proportionate to the overall dimensions of the flag.