I had an E46 328i Titanium and the paint kit from BMW for that exact color. I used it as indicated but for a rock chip but the result was AWFUL ! Although the color matching was not bad, the big problem is that with such a kit you do not put the same chemicals products to protect the paint as they do in factory, and thus the paint doesn't reflect the light the same way as the original one at all ! The rock chip was more visible after !!
--> DO NOT USE IT, YOU WILL REGRET IT
(or only prehaps on plastic spoilers)
Thanks for your input. My E39 M5 happens to be Titanium Silver! My concern is rust. Has anyone else had the same negative problem or experience? If so, short of going to a body shop, is the BMW touch up kit completely useless?