Let me save you some reading at that site.
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I FOUND BLUE-TINTED HALOGEN BULBS AT MY LOCAL RETAIL AUTO PARTS STORE. THE BULBS WERE MARKED AS BEING DOT APPROVED. ARE THESE OK?
No. This marking is fraudulent for two reasons:
•There is no such thing as "DOT approved". DOT does not "approve" products as the European regulatory body does.
•Semantic questions aside, the relevant regulations (US Federal Motor Vehicle Safety Standard 108, Canadian Motor Vehicle Safety Standards 108 and 108.1, and ECE Regulations 5, 6, 8, 20 and 37, all call for "white" light, defined as discussed above, so the statement of DOT compliance itself is false.
THEN WHY ARE SO MANY MOTORISTS USING THE ILLEGAL BLUE BULBS IF THEY'RE SO BAD?
There are several reasons I have learned by talking to users of these bulbs:
•Because they have been confused by marketing claims for the blue bulbs which falsely and incorrectly equate the blue bulbs' performance with the very expensive arc-discharge headlamps found on top-line luxury cars. They have been led to believe that by replacing their car's proper headlamp bulbs with the blue-coated bulbs, their headlamps' performance will be increased. In fact, quite the opposite is true; their headlamps' performance is decreased by the use of blue bulbs.
The placebo effect is alive and well, however, and the motorist who pays $35 or more for a set of these bulbs often will continue to insist that his headlamps have been made "better". Some motorists have continued to insist that the blue bulbs' performance was better, even when the low emitted-light values are shown to them on a non-chromosensitive light meter in comparison to the readings from proper non-blue bulbs.
2) Because they believe that the blue light makes their car look "cool". This would fall into the same category as the dark plastic headlamp and taillamp covers that are snapped-up by certain drivers for their appearance "enhancement" value, despite the fact that these covers, like the blue bulbs, are illegal and dangerous.