Great.
It's bad enough that we have all those misaligned HID lamps out on the highways, now we have to endure them out on the trails.
I guess it makes perfect sense to blind the rider that's coming towards you, you may as well see what's about to kill you.
As for colour temperature (or degrees Kelvin)
2700- 3000 it typically what you will have in your home. Think the a-lamp light bulbs in your ceiling fixtures or table lamps. These are a very warm (orange/yellowish colour)
3500 degrees kelvin is typically the colour temperature found in most office spaces. More of a yellowish colour, but when illuminated on their own they appear to be white.
4100 degrees kelvin is used in a small percentage of commercial spaces, but is typically used in drug stores where they want to impose a more sterile look, but not too blue, can also be found in parking lot lighting other similar places.
5000 - 6500 degrees kelvin is a blueish/white (or typically called full spectrum lighting) and is clearly used in cars, and sleds to blind oncoming vehicles. It is also used in horticultural applications
CRI (or colour rendering index) is another factor of lighting, but for this topic not really relevant.
If you are going to start new and replace your existing halogen lighting system, then I would be looking at LED's.
The driver (or a ballast for lack of better description) is typically smaller and lighter than the ballast for HID's.
They aren't subject to the extreme colour sifts that are seen in HID, and since they are a diode and not a filament based lamp (in theory) will survive the bumps better, and therefor last longer.
In terms of "lamp life" LED's will last longer than you standard halogen and HID light sources, and because of the tighter beam control available to the LED's they will project further down the trail.
In almost all cases higher lumens translates into brighter light, but it all depends on how the light is channeled (or directed forward).
LED's much prefer the colder climates as their heat source is right at the t-junction of where the LED is seated on the board. A good LED fixture should have a good heat sync. If it doesn't have a good heat sync, then you are just wasting your money.
LED's however start to lose their intensity almost from the first moment you turn them on, so even though they may rate them for 50,000+ hours, the initial lumens start to drop immediately.
just for the love of god......or fellow riders, stop using the "blue" lights, and get a professional to install them so that they are aimed properly.
I know you think you can do it yourself, but honestly......most of you can't.