Hi,

I'm checking to see if the mouse is over a rectangle. If it is, then it should make the box blue. Here is the code of that class, note that I do get a mouse clicked response.

 final int BLUETOOTH_TEST_BUTTON_X = 100;
 final int BLUETOOTH_TEST_BUTTON_Y = 100;
 
 final int STANDARD_BUTTON_WIDTH = 80;
 final int STANDARD_BUTTON_HEIGHT = 40;
 final int STANDARD_BUTTON_COLOR = 255; //Standard button color is white
 final Color MOUSE_OVER_BUTTON_COLOR = Color.green;
 
 boolean testButtonMouseOver = false;
 
 
 //Checks to see if the Test button is clicked, if so it will send a signal via
 //Bluetooth to turn on the LED test button
 void checkTestButtonClick()
 {
   //println("Button Click Tested!");
   
   if (mouseX > BLUETOOTH_TEST_BUTTON_X && mouseX < BLUETOOTH_TEST_BUTTON_X + STANDARD_BUTTON_WIDTH &&
   mouseY > BLUETOOTH_TEST_BUTTON_Y && mouseY <  BLUETOOTH_TEST_BUTTON_Y + STANDARD_BUTTON_HEIGHT)
   {
     println("Test Button CLicked!");
     
     myPort.write('A'); // Sends 'A' char to on board computer to be processed and interpreted
   }
 }
 
 void checkTestButtonMouseOver()
 {
 if (mouseX > BLUETOOTH_TEST_BUTTON_X && mouseX < BLUETOOTH_TEST_BUTTON_X + STANDARD_BUTTON_WIDTH &&
   mouseY > BLUETOOTH_TEST_BUTTON_Y && mouseY <  BLUETOOTH_TEST_BUTTON_Y + STANDARD_BUTTON_HEIGHT)
   {
     println("Test Button Mouse Over!");
     testButtonMouseOver = true;
   }
 }
 
 
 void draw() //Draws all things related to bluetooth
 {
   if (testButtonMouseOver)
   {
     fill(0, 102, 153);
   }
   
    rect(BLUETOOTH_TEST_BUTTON_X, BLUETOOTH_TEST_BUTTON_Y, STANDARD_BUTTON_WIDTH, STANDARD_BUTTON_HEIGHT); //Draw Bluetooth Test button
    //fill(STANDARD_BUTTON_COLOR); //Fill button
   
 }

Both the draw() and the checkTestButtonMouseOver() are called from the same place, and the checkTestButtonMouseOver() is called 1st.

Why is the box not changing color?

These are called from:

void drawBluetooth()
{
 
 bt.checkTestButtonMouseOver();
 bt.draw();
}

which in turn is called from setup().

And setup() is only called once: when your sketch starts.  Try moving drawBluetooth() into the main draw() loop...