JPasswordField KeyPress string length error?

I am trying to change background colors of a JPasswordField in Java Swing (Netbeans).

Here's what I have:

private void pstxtPasswordKeyPressed(java.awt.event.KeyEvent evt) {                                         

    //Get string from password box
    userPassword = new String(pstxtPassword.getPassword());

    //If password is 8+ characters
    //(one less because string counting begins at 0)
    if (userPassword.length() >= 7) {

        //Set password input box background color to green
        pstxtPassword.setBackground(Color.green);
    }

    else { //If password is less than 8 characters

        //Set password input box background color to red
        pstxtPassword.setBackground(Color.red);
    }

}

Everything works, except when I backspace. When I backspace after typing 8+ characters, the color doesn't change back to red until there is only 5 characters left in the field.

Help would be appreciated, I am very new to java programming and Netbeans.

EDIT: I have changed my code,

    //If password is 8+ characters
    if ((pstxtPassword.getPassword()).length >= 8) {

        //Set password input box background color to green
        pstxtPassword.setBackground(Color.green);
    }

    else { //If password is less than 8 characters

        //Set password input box background color to red
        pstxtPassword.setBackground(Color.red);
    }

This code seems to make sense to me, but in testing, the color changes green at the 9th character; when backspacing, it changes back to red at 6. This seems to be the same problem I had when the code was >= 7 where the color changed green at the 8th character, but changed back to red at 5 characters.

After typing 9 characters, the component turns green

After backspacing (starting from 9), component remains green until there are 6 characters

This is strange, because I have similar code in a button in this program which displays an error message. That code works fine. Is this a KeyPress problem, perhaps something to do with the backspace key?

As an aside, examine the length of the array returned by getPassword(), rather than the length of a String constructed from that array. The String is a security risk, as it will be stored for an indefinite time with the easily found name userPassword.

Addendum: Here's a related example of Robin's suggestion to use DocumentListener. I'm guessing that your key listener is seeing the KeyEvent before the JPasswordField has processed it.