checkable item of QTreeView doesn't obey the stylesheet with "windowsxp" style

With the WindowsXP style and the following stylesheet set for the application, the checkbox of a checkable item will not be transparent as it is with the other styles, e.g. "windows":

QTreeView {
background-color: rgba(255, 0, 0, 255);
selection-background-color: rgba(0, 0, 0, 255);
border: 0px;
}