The Display Settings
The display settings dialog is accessible through the Main Menu, then "Options", then "Display Settings" entry :

It is made of nine tabs, and each tab allows to configure the display appearance of a category of items :
1 - Atom and bonds style
2 - Atom colors
3 - Lights position and colors
4 - Critical points and bonds paths
5 - Various stuff like background color, atomic axis system arrows etc...
6 - Atom and critical points labels
7 - Constrains on electron density
1 - The
first tab is used to change globally the atom drawing style (lines or
ball and sticks) and to configure the lines width or the balls and
stick sizes and resolution. The probability and principal axis
appearance and colors of thermal displacement ellipsoids can also be
changed from this tab :

2 - The
second tab allows to change the color attributed to every chemical
specy, including special ones as "dummy atoms", "virtual atoms". It
allows also to globally configure atom colors using B factors for
instance.
3 - The
third tab is used to modify the position and color of the main
light source, and to add a second one if needed. The reflectivity
property of material can also be changed from this tab. To see the
effects of lights modification one must be sure a corresponding
material is displayed, as ball and stick mode or a 3D isosurface.

4 - The
fourth tab gives options to modify the appearance or visibility of
critical points, bond paths and curvatures. It change globally all
critical points by categories (3,-1), (3,+1) etc... The CP size
parameter is only active when the critical points are displayed in
"ball and stick" mode.

5 - The fifth tab
corresponds to various parameters. It change the background,
measurments (distances ...), selections marks and various tools colors.
Also the definition and orthogonal atomic axis systems arrows colors
and the "fog" color. This latter by defaults is synchronized with the
background color.

6 - The sixth tab
allows to configure viewer text, such as atomic and critical points
labels font, composition and color, and measurments font and color.
Composition means that an atomic label can be made of any combination
of parameters, separated by "-", "_" or a blank character. Example :
CB_3-0.5 is composed of atom name, "_", fragment number, "-" and
occupancy.

7 - The seventh tab
is used to change the way valence, multipolar or kappa constrains are
displayed on the viewer. For the moment three methods can be used : by
colored spheres or toruses so that one constraint scheme corresponds to
one given color, with the reference atom highlighted. The third method
is based on using two colors scheme, the reference atom being
surrounded by a red sphere, and the constrained atoms by a green sphere.
