QColorDialog::setStandardColor and QColorDialog::setCustomColor support alpha channel (rgba) but in implementation of both of them (where QColorDialogOptions fucntions have been called) the developer not considered that QColorDialogOptions::setStandardColor and QColorDialogOptions::setCustomColor only support rgb.

Therefore the output of QColorDialog::standardColor and QColorDialog::customColor not as same as input of QColorDialog::setStandardColor and QColorDialog::setCustomColor when we have alpha channel.

void QColorDialog::setCustomColor(int index, QColor color) 
{
     QColorDialogOptions::setCustomColor(index, color.rgba()); 
}
void QColorDialog::setStandardColor(int index, QColor color) 
{ 
   QColorDialogOptions::setStandardColor(index, color.rgba()); 
}
void QColorDialogOptions::setCustomColor(int index, QRgb color);

void QColorDialogOptions::setStandardColor(int index, QRgb color);