I have been looking for a 'true yellow' bulb like the old Hella Yellow Star bulbs which are no longer made. I want them for the C230 and the 300E. I installed the Phillips All Weather bulbs as H3s in my w124, and they are not really true yellow. The most that can be said is that they are more yellow than standard halogen white. They are actually a bit more yellow than old style non-halogen headlights, but not any where near as yellow as the Yellow Stars, or the old style yellow fog lights that came with the US lights on my w124 or my brothers w123.
There are several Korean bulbs out there with the true yellow light spectrum, but I haven't found any that are less than 70 watts, and have heard that they don't last long. (may be true: they are $20 a bulb at many places, but lots of shops have them of sale or clearance for $8-10; usually a sign of problems of some kind.)
If you are looking for improved fog performance - less scatter - the Philips will be a step in the right direction. If you are looking for lighting color effects, 'cat eye' headlights, etc. you probably won't see a major difference, IMHO.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E