Holy Martyrs of Constantinople
March 30
Roman Martyrology: Commemoration of many holy martyrs, in Constantinople, at the time of Constantius, by order of the bishop Aryan Macedonio, were sent into exile or tortured with unprecedented kinds of torture for refusing to abjure the orthodox faith.
Source: Santi e Beati, Catholic Online
I believe the picture you have paired with this post is of the Martyrs of Korea, not the Martyrs of Constantinople.