1819 the Tzar Alexander I gave the Finnish regiments their own flags. They show clear Preussian army traditions in their shapes, and they differed from the Russian flags by a heart emblem, and that the coat of arms was the Finnish lion instead of the Russian eagle.
The ships got their own flags, and 1883 the flag (red, white or blue with Russian flag in one corner) was changed to blue-white cross flag. 1899 the flags were ratified.
1863 a doctor from Oulu, Fredrik Nylander started to write about Finnish flag. Sakari Topelius had a small party the same year, and after that the flag was talked everywhere. There were a couple of different propositions - Topelius thought that the blue and white would be best, Nylander thought that it would be best to have the Finnish lion emblem as a flag, and the biggest newspaper, Helsingfors Dagblad suggested a red-blue-yellow flag. Everyone had a proposition.

The Russians didn't like this discussion. 1889 in the World Fair at Paris, the people discussed a lot about that two different flags were used - the Russian banner and the Finnish, inofficial flag.
1893 the Russian government wrote to the Finnish senate and told them that they may use only the official flag as given 1883, and 1896 the Tzar signed a declaration to forbid all the other flags except the Russian one, in official situations. This silenced the discussion about the flag, until 1905, after the great streak, when people raides the lion flag again. With the Russian revolution, the Russian flag was gone.
The lion flag was accepted as Finnish flag, but the commerce flag was discussed a lot - the senate couldn't agree, and when the civil war broke up, the flag discussion was postponed. After the civil war the blue and white flag was ratified - the state flag has the coat of arms in the middle, and the commerce flag is without. The flag law was confirmed 29th of May 1919.