Official Mr. Hobby/GSI Creos Gundam Marker set, produced to paint the "Mobile Suit Gundam: Iron-Blooded Orphans" series model kits representing Gundam Barbatos (suitable for any gunpla, anyway!).
GM161 - Gundam Barbatos White, armor base color;
GM162 - Gundam Barbatos Red, for details such as feet and decorations on the shoulders;
GM163 - Gundam Barbatos Blue, for details such as the chest armor;
GM164 - Gundam Barbatos Yellow, for details such as the tiara, and some parts on legs and arms;
GM165 - Gundam Barbatos Gunmetal, for the majority of unarmoured components;
GM20 - fine-tip black marker for panel lining.
The colored markers ink is alcohol-based, permanent and dries quickly. Obviously, it's particularly suitable for gunpla plastic parts. In case of mistakes or smudges, it can be wiped away using rubbing alcohol or the GM300 Gundam Marker (sold separately).
The fine-tip marker ink is water-based, and can be applied directly over painted parts after the paint is dry (to be extra safe, you can spray a layer of clear gloss over the painted parts). This marker is used mainly to panel line the models, i.e. to ink the grooves of gunpla armors putting them in evidence and giving them a feeling of higher thickness and a more realistic look. Excess paint can be removed rubbing it with the tip of a cotton swab, an eraser or the corner of a clean tissue.
Gundam Markers are produced in exclusive by GSI Creos and constitute one of the simplest, fast and fun methods to color gunpla models or add details.