Now it's getting close to winter people start to realise how poor their lights are compared to the latest generation of cars. A popular upgrade is to fit xenon headlight bulbs which give a 'whiter' light. Genuine xenon bulbs will improve the light output as well as apperance of your headlamps. Please note: No bulbs that I have come across will give the same appearance as HID (high intensity discharge) lamps as fitted standard to high end cars like mercedes,bmw and audi's - this is down to the construction of the headlight itself - if you buy bulbs expecting the same effect you will be dissapointed!
The bulbs will have a colour tempearture rating (xxxx K), and is a measure of the 'whiteness' of the light emitted - it has nothing to do with the operating tempearture of the bulb (ie how hot to the touch the bulb is). The lower the xxxx number is (say 3300K) the 'yellower' the light is, the higher the number (say 6000K) the 'bluer' the light will be, but the trade off is that the light output will appear to be less due to blue light being difficult to see by because our eyes are more sensitive to the yellow end of the spectrum - a 50W blue bulb will appear dimmer than a 50W yellow bulb due to our eyes sensitivity. In wet conditions the water actually absorbs a lot of the blue light so the light output will appear even lower.
Note: The colour temperature of natural daylight at noon is between 5000-5500K.
So blue bulbs may look cool but if you want to see where you are going, and others to see you, avoid them like the plague!
A couple of points to note are:
1) Check the level of your lightbulbs, the higher the level the more it will dazzle other motorists (Should only be used when towing & is illegal in some parts of Europe), you should ideally set it between low & medium (Your best of trying different options).
2) Keep the headlight glass clean - you'll be amazed how a quick wipe will improve the light output (Carry a packet of wipes from £1 shop)
3) If you change to xenon headlight bulbs you may want to change your sidelights too, but beware of LED bulbs, their light output is generally low, not very white and tends to be in one direction only.