Got an exhaust problem!!
 

what does it mean if your exhaust pipe's tip is covered by some lime green substance

What color is the coolant?

If it's not BMW blue and filled with yellow/green it may be coolant.

need info on vehicle

Your X5 has been abused by a leprechaun .No really,I have know idea.

Thats odd, all i can think is incorrect coolant or the junk from the oil seperator/ccv blowin out

Im gonna go with 3.0i from the single tip & exhaust cut-out trim ring?

Have you noticed it burning coolant?

While you clearly have something on the edge of the tips...I'm not so sure it's coolant or oil being burnt out, as the inside of the tips look to be dry. Secondly, looking at that bumper makes me wonder if whomever refinished it, did so with it on the vehicle. From the pic you provided, if you look closely, between 7'oclock & 830 positions it looks like that "buildup" is flaking off...kinda looks like whatever was sprayed onto the bumper (and is flaking) was also sprayed onto the tips and is now burning/flaking off them as well.

Ok that is some strange shit. Maybe you backed up into some bushes or something. And i agree with x5snd, your tip seems to be peeling.

First of all those tips are dirty as shit. Get some 0000 steel wool and some polish and go to town cleaning them up. When done and polished, if the green stuff comes back you have a problem

Umm the pollen sticking to it...?

Agreed with RB...that tip look dirty....lol...:popcorn::popcorn::stickpoke