customize textbox color outline

nope , but you can put the text field inside a card and change the background color of card according you your need

 a!cardLayout(
            contents: {
              a!textField(
                label: "",
                labelPosition: "ABOVE",
                saveInto: {},
                refreshAfter: "UNFOCUS",
                validations: {}
              )
            },
            height: "AUTO",
            style: "ACCENT",
            marginBelow: "STANDARD"
          )