A false H4 yellow refers to a car bulb designed to resemble an original H4 bulb but fails to meet legal standards and regulations. These bulbs may be unauthorized because they might not offer the same brightness, light color, or durability as approved lamps. They are often sold as cost-effective alternatives to branded products. Using such bulbs can lead to safety risks on the road, such as reduced visibility or glare for other drivers. It is important to look for certifications and approvals when purchasing replacement bulbs.