Using an Intel graphics card (if relevent), the radial gradient inverses the 
colors in presentation mode when using the Graphics Output -> Use hardware 
acceleration option.

Procedure for reproducing the problem:
-> activate the "Use hardware acceleration" option in:
 Tools -> Options... ->OpenOffice.Org -> View -> Graphics Output
--> Open a new presentation
--> Create a fillable object: ex rectangle
--> Set Area Style/Filling of object to Gradient
--> Choose a radial gradient (ex: Radial red/yellow)
Observe result in the editing mode and in presentation mode.
The results are different.

PS: this problem could be intel driver dependent: I have no means of testing 
that...