OFFICIAL ADOPTION OF THE FLAG
The French National Convention adopted as national flag the three colours blue, white, red on 15 February 1794 - or more exactly, on 27 pluviôse an II in the revolutionary calendar. The decree says (in my own free translation):
II. The national flag shall be formed of the three national colours, set in three equal bands, vertically disposed so that the blue is attached to the staff of the flag, the white in the middle, and the red flying in the air.
III. The jacks and the daily ensign are formed in the same way, observing the size proportions established by custom.
IV. The commissioning pennant shall be also formed of the three colours, with one-fifth blue, one-fifth white, and three-fifths red.
DESIGN OF THE FLAG
The Tricolore flag was created in 1790 but with the colours the reverse of what they are today, i.e. with red at the hoist, and revised in 1794 to the modern form. The 1790 flag existed only as part of the jack and ensign of the navy.
COLOURS OF THE FLAG
The colors of the French flag "combine" different symbols, invented after the fact:
Blue is the color of Saint Martin, a rich Gallo-Roman officer who ripped his blue coat with his sword to give one half of it to a poor who was begging him in the snow. This is the symbol of care, of the duty that the rich had to help the poor.
White is the color of the Virgin Mary, to whom the Kingdom of France was consecrated by Louis XIII in the 17th century; it is also the color of Joan of Arc, under whose banner the English were finally driven out of the Kingdom (15th century). It became logically the color of Royalty. The King's vessels carried plain white flags whilst at sea.
Red is the color of Saint Denis, the saint patron of Paris. The original oriflamme (war banner) of the Kings was the red oriflamme of Saint Denis.
Most French flags, at least in the beginning of their use, have a very dark blue shade, sometimes called bleu drapeau (flag blue). Petit Larousse Illustré has nothing on bleu drapeau, but has :
Bleu roi: bleu soutenu (celui du drapeau francais), i.e. King blue: strong blue (the blue of the French flag)'.
Therefore, it seems that the use of a dark blue for the French flag has been widely accepted, since it is highligted to examplify the 'king blue' shade.
For the naval flags, the maintenance service of the French Navy (HCC) gives the following specifications (in reference to AFNOR standardNFX 08002):
Blue A 503
White A 665
Red A 805
Blue Pantone 282c and red 186c are my translation (approximation) of those colours.
NICKNAME OF THE FLAG
Nouveau Petit Larousse Illustré has for Tricolore the following entry:
Tricolore adj. (du pref. tri , et du latin color , couleur). De trois couleurs. Le drapeau tricolore, le drapeau français. - L'origine des trois couleurs qui figurent dans notre drapeau national remonte à l'année1789 : pour cimenter la bonne intelligence entre le roi et la ville de Paris, dans la journée où, suivant le mot heureux de Bailly, Paris reconquit son roi, on réunit à la couleur blanche, qui était celle de la royauté, le bleu et le rouge, couleurs qui figuraient dans les armes de la ville de Paris.
[Tricolore adj. (from prefix tri and Latin color, colour). Of three colours. Le drapeau tricolore: The French flag. - The origins of the three colours figuring on our national flag go back to year 1789: In order to create a good relation between the King and the city of Paris, on the day where, as Bailly expressed it rejoicing, Paris reconquered its King, the colour white, which was that of royalty, was associated with blue and red, which are colours figuring in the arms of the city of Paris.
Peter Hans van den Muijzenberg, 26 September 2001
CIVIL ENSIGN

Flags proportions
The proportions of vertical stripes on the French flag when used at sea as the civil or naval ensign or jack are 30:33:37, to give a good visual effect when flying, and therefore called optical proportions.
The Tricolore ensign was adopted by decree dated 27 pluviôse an II (15 February 1794) and by decree dated 7 March 1848. The proportions 30:33:37 were decided by regulation dated 17 May 1853.
The regulation of 1853 gives the precise measurements, in metres and centimetres, of the standard legal ensigns, sizes are numbered from 1 to 16.
#1 = 9 m x 13.5 m
#16 = 50 cm x 75 cm.
When hoisted vertically, the French national flag is very often forked.
MASTHEAD PENNANT

Naval Masthead
The masthead pendant in its present form (replacing the interim design adopted on 24 October 1790), was established by Article IV of a Decree of the National Convention dated 27 Pluviose of the Year II (15 February 1794). The Decree gave the construction details of "one-fifth blue, one-fifth white and three-fifths red", while the table of standard sizes were confirmed by Naval Regulations issued in April 1987.
The masthead pennant is a triangular tricolour pennant, proportion
1:20 or 1:(4+4+12)
OTHER FLAGS
Almost no private individual in the Languedoc flies the French Tricolore flag, though many fly the flag of the old Counts of Toulouse, ith the famous Cross of Toulouse. Even some mairies will fly this flag along with the tricolore and the flag of the European Community.
A minor footnote: The annual `rent' paid by The Duke of Marlborough to the English Crown for the royal manor of Woodstock and Blenheim Palace is a Royal French flag, "Argent three fleurs-de-lys Or". The Duke of Wellington pays a similar rent for his property, also granted in recognition of military victoty, but each year he presents the later French flag, a tricolore.