At the time of Alexander III of Russia, the official interpretation was as follows: the white colour symbolizes nobility and frankness; the blue for faithfulness, honesty, impeccability, and chastity; and the red for courage, generosity, and love. A common unofficial interpretation was: Red: Great Russia, White: White Russia, Blue: Little Russia.
The federal constitutional law of the Russian Federation only says that the colours of the flag are "white", "blue" (синий, or dark blue, as Russian has two colours that are called "blue" in English), and "red". The Federal Constitutional Law on the State Flag of the Russian Federation does not specify which shades the colours should be.