Where can I purchase Light grey or MB stone color ABS filament in the US?

Not exactly sure the shade of grey you are looking for, but check MicroCenter, if you have one close by they are pretty cheap on some of their filament. Not to sure on the ABS, but they have PLA for $15 a roll, it is all i use, and have had no issues with it.

Hey @RCR72, make sure to add some tags to your post so that the post reaches the relevant people. I have added Washington and Filament