Return a go2color dict containing GO colors determined by P-value.

def get_goid2color_pval(self):
        """Return a go2color dict containing GO colors determined by P-value."""
        go2color = {}
        self.set_goid2color_pval(go2color)
        color_dflt = self.alpha2col[1.000]
        for goid in self.go2res:
            if goid not in go2color:
                go2color[goid] = color_dflt
        return go2color