in javascript any object is a hash table, to set or get style properties I can

if (node.style.color === "blue")
  node.style.color = "red";
else
  node.style.color = "blue";


Try doing the same using JFX API;

The same, incomlete

String key = "-fx-fill:";
String style = text.getStyle();
int index = style.indexOf(key);//assume is always there;
int endIndex = style.indexOf(";", index);//assume is always there
String value = style.substring(index + key.length(), endIndex).trim();
String newStyle = style.substring(0, index) + style.substring(endIndex + 1);
if (value.equals("red")) {
    newStyle += "-fx-fill: blue;";
} else {
    newStyle += "-fx-fill: red;";
}
text.setStyle(newStyle);