* Set cell color. This sets some associated values; for finer control
* you may want to access these elements individually.
* @param rgbStr - the desired cell color, in the hex form "RRGGBB".
*/
public void setColor(String rgbStr) {
CTTcPr tcpr = ctTc.isSetTcPr() ? ctTc.getTcPr() : ctTc.addNewTcPr();
CTShd ctshd = tcpr.isSetShd() ? tcpr.getShd() : tcpr.addNewShd();
ctshd.setColor("auto");
ctshd.setVal(STShd.CLEAR);
ctshd.setFill(rgbStr);
}