Roughly described, a system enables quick and accurate depiction to a user of multi-patterning layout violations so that they may be corrected manually and in real time, and without interfering with normal manual editing process. In one embodiment, the system involves iteratively building tree structures with nodes identifying islands and arcs identifying multi-patterning spacing violations between the connected islands. The system detects coloring violations during the building of these tree structures, using the relationships previously inserted. The coloring violations preferably are reported to a user in the form of visual indications of the cycles among the candidate spacing violations, with the candidate spacing violations also themselves indicated visually and individually. The user can see intuitively how to move the islands around, and in which directions and by what distance, in order to remove a multi-patterning spacing violation and thereby break the cycle.