Been there, done that. Some pens it may not matter, I have done both yellow and orange colors as well as some black with gold that it was no big deal. Other colors it is a pain. The now presume the tube will show and ask if I am concerned before gluing the tubes in.
I was going to use it with an Elegant Monarch pen in Blue Galaxy finish. So I'll use this one on a cheaper pen, and use the other half of this blank for the Monarch. Only this time I'll back paint it and paint the tube.
***Mix and Match any Group A Kits for the Quantity Discounts*** Elegant Monarch Pen Kit Compare to Sierra and Gatsby Pen Kit Specs-5.25 inches long (133mm)1.5 oz (approximate)Drill needed, 27/64"Brad point Drill Bit / Twist Drill BitSingle Kit Includes--Pen Kit-Tube-Parker Style Ink Refill For...
Acrylic blanks take a beautiful polish that gives the appearance of a liquid tube. Blanks turn and drill easily. No topcoat finish is necessary. Moonlit Ocean Acrylic Pen Blank measures 3/4" x 3/4" x 5".
For almost all of the opaque acrylic blanks I use, I paint the tubes knowing that there is a good likelihood of the tube showing through. White usually helps out quite a bit, but I purchased a few other colors of spray paint and use them as needed on the tubes. I know many customers won't mind, but it always bothers me. The only time painted tubes won't help is with the very light colored blanks. For those I use white on the tubes.
That’s what I do when worry about blank transparency. I’ve even tinted the epoxy with casting dye while flying in the tube, as a 3 rd precaution. Some would say a bit overkill but sometimes the tube edge scratches the paint off the hole so the painted tube and epoxy were just the backup plan for success.