Gold Star is really that: A perfectly glowing golden … errr … gold. It is the most gold looking ink I am aware of and it did perform well even in a flexible nib such as the FA in a Pilot Custom Heritage 912.
I had the ink in the pen for well over two months and still had no problems with a clogged feed. I did notice, however, that after washing out the ink and even after a bath in an ultrasonic cleaner the next fill of a red ink did have some shimmer to it. This, I gladly repeat it again and again, is the most dangerous “risk” shimmer inks will pose. Of course, putting ink with shimmer particles in a very precious and hard to clean vintage pen would be something even I would avoid, but in modern pens such as the cartridge/converter CH 912, there is nothing to fear. These inks do rinse out fairly easy.