Here's how I refill my Pentel Color Brush Pen. For black, I use Rotring ink. If you want colours, you can try Dr. Ph. Martin's Hydrus Watercolor.

Blunt needle and syringe:
https://www.amazon.com/gp/product/B01...

Hydrus watercolor:
https://www.amazon.com/s/ref=nb_sb_no...

Rotring ink:
https://www.amazon.com/rOtringIsogra...

Pentel Color Brush Pen review:
http://www.parkablogs.com/content/rev...

The links to Amazon are affiliate which means I earn some commission whenever a purchase is made through referral.

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