Fog light bulbs in the euro omegas are H1s I think, here in the states we use H3s dont know why but thats how they are.
There are two kinds of bulbs, Halogen and HID(high intensity discharge)
THe halogen are rated by ex. 55w, or 65w or 100w depending on how much power they require in order to run...
The HIDs are all 35W but produce 3x more light.
They are rated at 3000k, 4300k, 5000k, 6000k, 8000k, 10000k etc... and thats the color of the light, the higher the number the more blue purple the light becomes and the less actual light being produced....
3000k uses a filter to make the color yellow, and the 4300k gives the most amount of light.
Halogen bulbs the clear ones make around 1000lumens of light, and the HIDs 4300k make around 3200lumens of light so you judge the difference...
A blue coated halogen bulb that was rated at 55w will make around 30% less light then the same non coated bulb but will look like its brighter...
Hope that helps!