Here is the OE part number for the front turn signal on the E53 - 63217160897.

The part is called SILVER BULB, when in hands, looks yellowish/silverish, once installed, the corner looks bluish... I've had it on my E39 for years - back then you could not buy it from US dealer, so I got it in France, cost me like 50-60 Euros for 4 of them... Now you can get them from a local dealer...

The BMW of Fairfax has them for $11 apiece...

I will snap a pic of my tails later today and post here...