Yep asthetically, next to the bright pure white HID's they look awful.
When the sidelights and dipped beam are on together the side lights are plainly visible as they are in separate light clusters from the dipped.
I know this in an old-ish post, so you may have found a solution already.
I bought an E320 (W211) a couple of weeks ago, and the first night I drove it, I realised how bad the Xenons looked compared to the yellow/cream sidelights. The next day I bought some capless LED bulbs to put in (as I have done on my other cars), but the Mercedes didn’t like them! It showed on the dash that the bulbs were not working, and I presume it’s due to the LED’s drawing so little power, that the system thought there was a blown bulb. Also when I turned all lights off and ignition, the LED’s were still on - again I think the bulb test system must send a small amount of power down the line to test, and was lighting up the LED. (I could be wrong, the Mercedes system may not work like that, but that’s how it appeared to me)
I’ve found some 12 volt 5 watt capless bulbs that are designed to match the colour of the Xenons - the glass on the bulb is painted blue, but they light up white. They still don’t match the blue/white light of the Xenons, but look much better.
I might try adding another bulb holder near the sidelight holder, so I can have a traditional type bulb in that one, with it secured out of sight, then put the LED in the normal sidelight holder, so I get the look of the LED, and a similar power usage for the bulb test function. (There may be a better way of doing this, but I’m no electrical expert!!)
Next on the list to do, is change the main beam bulb, for a white/blue look, as I don't like when you are driving on dipped beam, then put on full beam, you can see the yellow beam above the white/blue beam - it would be better if itall matched
