While headlight bulb fitment has not changed in 15 years, the technology inside the bulb has changed. New coatings, filaments and gases have made headlight bulbs brighter. But, these advancements have changed the color of the light produced by the bulbs. Replacing just one bulb at a time can cause differences in light output and appearance of the headlight. This is why replacing bulbs in pairs is a best practice for shops and drivers.
Replacing just one bulb can cause differences in light output. This video is sponsored by Auto Value and Bumper to Bumper.