So long, purple streetlights. Only a handful of the lights remain on Wisconsin interstates.

UPDATE: The Wisconsin Department of Transportation said more purple streetlights appeared in the summer of 2023. Click here to read the latest.

The manufacturer that provided the defective purple streetlights along Wisconsin highways and interstates has paid all costs associated with replacing the lights, the Wisconsin Department of Transportation said.

Less than 100 purple streetlights remain in Wisconsin after popping up around the country two years ago, during the spring of 2021. Many drivers began to notice that highways and interstates were taking on a new purple hue lighting scheme.

Despite the popularity from the public, the DOT announced the lights were defective and were going to be replaced.

The DOT installed a batch of LED lights in 2018, mostly in the southeast region. At least 300 lights began changing color from white to purple. The effect would lead to interstates being lit purple at night where these lights were highly concentrated.

When the DOT announced it was removing and replacing the lights, a number of people reached out to the Journal Sentinel, saying they preferred the lighting scheme. Some readers said it was easier on their eyes late at night while others thought purple was cooler than white.

"SAVE THE PURPLE LIGHTS!" one reader texted.

At the time, a spokesperson with the DOT said, "We are not going to a purple-hued street lighting plan. ... I didn't imagine that anybody was going to become that attached to them." The department added that bright white lights are necessary to safely light the interstates.

According to the DOT, the reason the light-emitting diode (LED) lights transitioned from white to purple has to do with a phosphor coating around individual diodes. The coating is placed there because LED lights for highways employ a blue LED naturally and the coating is used to diffuse the blue light to white.

As the phosphor coating fails, it exposes the LED's blue color and the issue causes the lights to transition from white to purple over time.

The manufacturer that supplied the faulty lights is American Electric Lighting, a subsidiary of Acuity Brands Lighting. The DOT said American Electric Lighting paid all costs for the replacement of the faulty lights, including materials, labor and traffic control per product warranty.

Wisconsin wasn't the only state affected by the purple lights. Duke Energy, which installed the lights in some other regions, said likely thousands of LED lights were installed throughout the country that turned purple. Reports of purple lights occurred in Kansas, South Carolina, Illinois and Florida.

As of Friday, 86 purple lights remained along Interstate 94 from Seven Mile Road to Drexel Avenue, according to the DOT. These lights will be addressed in the coming weeks.

Contact Drake Bentley at (414) 391-5647 or DBentley1@gannett.com. Follow him on Twitter at @DrakeBentleyMJS.