如何设置grid某列的背景颜色

Ext.grid.CheckColumn.prototype ={
init : function(grid){
this.grid = grid;
this.grid.on('render', function(){
var view = this.grid.getView();
view.mainBody.on('mousedown', this.onMouseDown, this);
}, this);
},

onMouseDown : function(e, t){
if(t.className && t.className.indexOf('x-grid3-cc-'+this.id) != -1){
e.stopEvent();
var index = this.grid.getView().findRowIndex(t);
var record = this.grid.store.getAt(index);

var en = {
grid: this.grid,
record: record,
field: this.dataIndex,
value: record[this.dataIndex],
cancel:false
};

if(this.grid.fireEvent("beforeedit", en) !== false && !en.cancel){
record.set(this.dataIndex, !record.data[this.dataIndex]);
}

}
},

renderer : function(v, p, record){
p.css += x-grid3-check-col-td';

return '