You can add code to the reset button click event to set the colour back to the background colour of the form. For example, the following code checks if the border fill colour is "51,153,102" (green). If it is, set it to "255,255,255" (white).
//form1.page1.subform1.resetBtn::click - (JavaScript, client)
xfa.host.resetData();
if (xfa.resolveNode("form1.page1.subform1.bar.ui.#textEdit.border.fill.color").value == "51,153,102") {
xfa.resolveNode("form1.page1.subform1.bar.ui.#textEdit.border.fill.color").value = "255,255,255";
}
Steve