Sorry to drag up an old thread but i've just experienced the same thing on my newly purchased F10 M5.
The car recently had a coolant leak which is now fixed but I thought I should check the coolant colour before I added the regular BMW blue stuff I got from my local BMW dealer.
Now one thing to note here is that my car had a new engine a couple of years back (late 2018) and i know BMW now have a green coolant (HT-12) that is used in newer vehicles.
I'm wondering if you had/have and I have the newer coolant? FYI in real life it looks almost like the colour of olive oil so not orange more green.
Pics of the stuff i just pulled here:
https://ibb.co/j3zNQkk
Thanks in advance all!