Solution:

1) To change graph colors for all graphs in a presentation:

a) Select the 'Format' menu and select 'Slide Color Scheme...'. (The Color Scheme dialog box appears.)
b) To change the entire color scheme:

1] Click 'Standard' tab.
2] Select a new color scheme from the 'Color Schemes' group.

c) To change only individual graph colors:

1] Click 'Custom' tab.
Scheme Colors
2] Select the desired specific color to change from the 'Scheme Colors' group.
3] Click 'Change Color...'. (The appropriate dialog box appears.)
4] Make the desired changes to the selected color .
NOTE: Differences between the current color and the newly selected or changed color can be seen in the 'New Color', 'Current Color' box in the bottom right corner of the dialog box.
Differences
5] Click 'OK'.

d) Do one of the following:

1] Click 'Apply to All' to apply the new standard color to ALL the slides in the presentation.
2] Click 'Apply' to apply the new standard color to the current slide only.
3] Click 'Cancel' to abort the slide color scheme change.

2) To change graph colors for one graph in a presentation:

a) Select the desired graph object. (Handles appear around the border.)
b) Select the 'Edit' menu and select 'Chart Object'. (A submenu appears.)
c) Select 'Edit'. (The Microsoft Graph Edit window appears.)
d) Select the 'Tools' menu and select 'Options...'. (The Graph Options dialog box appears.)
e) Click 'Color' tab.
f) Select the desired color to change.
g) Click 'Modify...'. (The Color Picker dialog box appears.)
h) Change the color as desired.
i) Click 'OK'. (The Graph Options dialog box reappears.)
j) Click 'OK'.