Aftermarket HID bulb swap help

[IamJanuar]

My friend got one of his aftermarket HID bulb out on his E430. The local shop told him that if he wants to replace the bulb, he needs to replace them with the same exact brand or it wont work. How true is this?
If this hold true, then it's bad news for him since he had thrown the box ages ago and the ballast has no brands on them. Furthermore, he bought them out of US. (some generic taiwan brand)
I have seen the set before he had them in and I have the impression that the bulb is a universal item since the bulb has wire and connector that look like any other I had seen.

[NISMOPOWERED]

The bulb will have a generic part number on it. As long as he matches that it will work. The brand doesn't matter.

[stox]

I have heard that you should replace HID bulbs in pairs due to their aging characteristics. Otherwise, one bulb will always look different from the other.

[NISMOPOWERED]

Colors can vary by age, brand, and each batch. I would just do the one and see if it matches. Most of the time you cant see any difference.

[IamJanuar]

I bet he is willing to buy a pair.
The big question is now whether any brand can replace these bulbs...