I recently had to convert a javafx.util.Color to its web representation.

What I ended up doing is, I used a substring of the toString() method and added the #.

String style = "-fx-background-color: #" + color.toString().substring(2, color.get().toString().length() - 2);

I also had to cut the alpha value.

It might be helpful, if there was a method on the color object which converts it to the web color.

Something like this:

Color color = Color.BLUE;
String webColor = color.toWeb(); // #0000FF