Official Mr. Hobby/GSI Creos Gundam Marker set, produced to paint gunpla models representing green or red Zakus (suitable for any gunpla, anyway!).
GM34 - Char Pink;
GM35 - Char Red;
GM36 - Zaku Dark Green;
GM37 - Zaku Light Green;
GM38 - Phantom Gray;
GM39 - Zeon Gray.
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).
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.