Blue is the color of the sky and sea. It is often associated with depth and stability. It symbolizes trust, loyalty, wisdom, confidence, intelligence, faith, truth, and heaven. Blue is considered beneficial to the mind and body. It slows human metabolism and produces a calming effect.
1 Backlash (sociology), an adverse reaction to something that has gained prominence.  Backlash (pressure group), a UK group opposing the 2008 law criminalising possession of extreme pornography.
2. backdraft. An explosive surge in a fire produced by the sudden mixing of air with other combustible gases. This is caused by a condition in a fire where oxygen is depleted and the fire dies down until a door is opened and the fire flares violently from the sudden intake of oxygen.