Legal tint in Colorado comes down to two numbers: non-windshield windows must allow at least 27% of visible light to pass through, and the windshield itself must allow at least 70%. Those limits, set by Colorado Revised Statutes § 42-4-227, measure the combined light transmission of the factory glass and any film on top of it, which is why a film that sounds dark enough on paper can still put you over the line.
How Dark You Can Go on Each Window
The baseline rule covers every window on the car except the windshield: front sides, rear sides, and the back glass all have to hit at least 27% Visible Light Transmission (VLT). That 27% is the total light reaching the cabin through the glass and the film together, not the number printed on the film’s packaging.
There is one exception worth knowing. The windows behind the driver, meaning the rear side windows and the back glass, can go darker than 27% as long as the front side windows and the windshield both allow at least 70% light through. This is how you get the common look of light front windows paired with a much darker back half. The exception applies to every vehicle type, not just SUVs or vans.
Windshield Rules
The windshield has to meet the 70% VLT standard across most of its surface. The law does allow a tint strip along the top four inches, and that strip can actually be nontransparent. It doesn’t have to meet any VLT percentage at all.
What the strip can’t do: it can’t be red or amber, can’t distort your perception of colors, and can’t bounce sunlight or headlight glare into other drivers’ eyes any more than clear glass would. Stay within four inches from the top and avoid those colors and you’re fine. The common assumption that the strip has to match the 27% standard used elsewhere on the car is wrong.
Why the Number on the Film Isn’t the Number That Counts
This is where most accidental violations happen. Factory automotive glass already blocks some light on its own, typically transmitting between 70% and 85%. When you add film, you multiply the two VLT values to get the net result that an officer’s meter will read.
Run the math on a common setup. If your factory glass transmits 74% of light and you apply a 35% VLT film, the combined reading is roughly 26% (0.74 × 0.35 = 0.259). That’s under the 27% minimum, even though a 35% film sounds like it should clear the bar with room to spare. A good installer will measure your factory glass first and work backward to pick a film that keeps you legal after the multiplication. If you’re doing this yourself, round conservatively.
Reflectivity and Color
Colorado flatly bans any window material with a metallic or mirrored appearance. This isn’t a “no more reflective than factory glass” rule. It’s a complete prohibition on metallic-look and mirror-finish films on every window, rear glass included. If you can see your reflection in the window from outside, the film likely crosses the line.
The red and amber restriction in the statute is written specifically for the windshield strip, because those colors could be confused with traffic signals or emergency lighting. The statute doesn’t single out red or amber film on other windows, but any material that affects perception of primary colors or otherwise distorts vision can trigger enforcement anywhere on the vehicle. Neutral gray, charcoal, or ceramic film sidesteps the whole question.
Medical Exemptions
Colorado’s § 42-4-227 does not contain a formal medical exemption, which surprises drivers coming from states that do. There is no official process for getting a doctor’s note that authorizes darker-than-legal tint. Some shops advertise medical exemptions based on practices from other states, so be careful with that advice. Carrying physician documentation during a stop might help as a practical matter, but it is not a legal shield against a citation.
Penalties
Driving with illegally tinted windows is a Class B traffic infraction, which carries a fine between $15 and $100. Court costs and surcharges push the real total higher. A Class B infraction adds no points to your driving record, so a tint ticket shouldn’t move your insurance rates the way a speeding ticket would.
Installers face stiffer treatment. Anyone who installs, covers, or treats a window so it fails the VLT requirements commits a Class A traffic infraction, which carries higher penalties than what the driver faces. A shop that knowingly puts on illegal film is risking more than you are.
Enforcement is objective. Officers use a portable meter that clips onto the window edge and reads light transmission directly, so there’s no estimating involved. The number on the meter is the number on the ticket. After a citation, you’ll typically need to remove or replace the non-compliant film and may need to show the court proof that you did.
Out-of-State Vehicles
If your car is registered somewhere else, Colorado still expects compliance, just at a looser threshold. Legislation passed in 2019 requires out-of-state registered vehicles operated in Colorado to allow at least 20% light through non-windshield windows. That’s more permissive than the 27% required for Colorado-registered cars, but a fully blacked-out vehicle from a state with no limit can still get cited here.
The 70% windshield requirement applies no matter where the car is registered. If you’re driving through with side or rear tint darker than 20%, the risk is real, particularly along the I-70 corridor and around Denver.