Hi Osborne yes on my project directory under style i do have infragistics styles. What i did after this post manage to work around my exisitng code. By doing the following steps;
1. created method under constructor. eg setStyle("C:\WorkSpace\Folder Name for IDE\OEProject\Styles-Folder\Pear.isl").
2. Create function called METHOD PUBLIC VOID setAppStyle(vStyle AS CHARACTER):
Infragistics.Win.AppStyling.StyleManager.Load(vStyle).
RETURN.
END METHOD..
3. This load themes and style when this logic had been applied, all the background color changed including buttons.
Thanks for the feedback