In an example, a virtual build volume comprising a representation of at least a part of an object to be generated in additive manufacturing is segmented into a plurality of nested segments comprising a core segment, an inner peripheral segment and an outer peripheral segment. Additive manufacturing control instructions may be generated for the nested segments. The control instructions for the core segment may provide a first region of the object corresponding to the core segment and having a first color. The control instructions for the outer peripheral segment may provide a second color for a second region of the object corresponding to the outer peripheral segment. The control instructions for the inner peripheral segment may provide a third color for a third region of the object corresponding to the inner peripheral segment, wherein a color of the third region is determined so as to at least partially visually mask the first region.