MacDev- picker view的外觀

我的picker view預設被選擇的那個row會是灰色的
https://imgur.com/a/FsHPQkW我想把它變成白色（無特殊樣式）
試著修改了viewForRow:forComponent也沒有用

let specificView = UIView.init()
specificView.frame = CGRect.init(x: 0, y: 0, width: 130, height: 45)
specificView.backgroundColor = UIColor.white

let specificLable = UILabel.init(frame: CGRect.init(x: 0, y: 0,
width: 130, height: 45))
specificLable.textAlignment = .center
specificLable.text = 'aaaa'
specificLable.textColor = UIColor.black
specificView.addSubview(specificLable)

return specificView

請問要怎樣才能把那灰色的背景顏色拿掉?

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