Hi Sabuj, There is no Chimera user inteface to set the unit cell outline box color or line thickness. You could edit the Python code chimera/share/UnitCell/__init__.py to get different color and thickness. Use any text editor and change line 186 from color = (1,1,1) # white to color = (.5,.2,.8) # outline color, (red,green,blue) To change the line thickness add after line 399 group.set_display_style(group.Mesh) group.set_use_lighting(0) group.set_triangle_and_edge_mask(hide_diagonals) the additional line group.line_thickness = 3 # In screen pixels. I've added to our requested feature list and item to creat a user interface in the "Unit Cell" dialog to make these settings. Tom