The flag of Martinique features a blue field on the hoist side and a white field on the fly side, with a red stripe dividing them diagonally from the lower hoist corner to the upper fly corner. The width of the red stripe is one-fifth of the total flag length, and its centerline is positioned two-fifths of the way up the flag's length from the hoist.

The aspect ratio of the flag is 2:3, meaning that for every two units of width, there are three units of height.

The specific color codes for the flag are as follows:

• Blue: Pantone 286 C (C=100%, M=60%, Y=0%, K=0%)
• White: N/A (the absence of color)
• Red: Pantone 186 C (C=0%, M=90%, Y=80%, K=5%)

The flag has no complex geometric properties or measurements beyond those described above.