Until the Revolution, French Navy ensigns were all white, while merchant ones used to display local or personal designs in the canton of an also white flag. The new regime just unified all previous designs under a common pattern: a white flag with a canton of three equal columns of red, white, and blue - these sorrounded by a blue and red border. Following the overthrowing of Louis XVI in 1794, the National Convention decreed a new Tricolor flag, with no white background at all, to serve as national flag and naval ensign of the Republic.
Sources: Wikipedia(en):French ensigns | Flags of The World (FOTW) website:French Revolution (1789-1799)
Sizes: ensign W12 x L18 mm, mast flags W8 x L12 mm, jack W6 x L9 mm, pennant W4 x L48 mm.