The tinting of a vehicle's window glass for either aesthetics or comfort is a very popular practice. The rules regarding how dark tint can be vary by state and location, and the reasons behind them may prove surprising.
Many states restrict usage of certain colors. These colors are most often red, blue, amber and yellow.
The reasoning behind the ban of certain colors is that they may make it impossible to discern the difference between the lights of emergency vehicles and the ambient light around them.
The main regulations on window tint are in regard to its darkness. Tint is rated by indexing the percentage of light it can block, so higher numbers mean darker tint.
How dark tint can be varies wildly from state to state and which window the tint is applied to. A tint's legality usually has less to do with driver safety, and more to do with a police officer's ability to see inside.
In general, darker window tint may be used on the side windows than the front or back. Check the "Tint Dude" link in Resources for the particulars of your state.
