The new identity cards went into effect Wednesday, the EUobserver reported.
Matthew Newman, a justice spokesman for the European Commission, said identity cards are a national responsibility. He said the European Union cannot intervene.
Under the old system, Finns carried light blue and foreigners light pink cards. The National Police said the two colors were hard to tell apart with a quick glance while the new deep blue and deep brown cards will be easy.
Finns are not required to carry ID cards. But they are convenient for proof of age and Finnish nationals can use them instead of passports in the Scandinavian countries and the EU.
Michael Privot, director of the European Network Against Racism, suggested the cards are a "subtle attempt to legalize ethnic profiling."
"Would blue be referring to the stereotypical eye color of Finns and brown to the skin color of foreigners? While there are so many colors available, such a choice definitely raises questions," he said.