To reply to your questions - no I used the standard brass tubes. I paint the insides of the holes - I know many people paint the tubes. Here is my theory on painting the hole - then the light reflects directly after the acrylic. Painting the tubes requires light to go through the acrylic, then the glue then hits the paint. On the way out it has to go through the glue again.
The color theory starts around the 2 minute 28 second mark. That video also explains the fifth pen - the purple. It is a bright purple blank.
Also found I needed to over drill the hole to accommodate the paint. The bottom was a perfect 10 mm and the top 12 mm (yes not 12.5). The pens look better in person - never claimed to be a photographer.