Red Color Code with Arduino Giga Display Shield

Official Hardware Mega GIGA Display Shield
1

I am trying to create a red rectangle with a Giga Display Shield using the color code 0xff0000 but it's coming up black. Here is the line of code:

#define RED 0xff0000

void setup() {
    display.begin();

    display.fillRect(0, 0, 800, 36, RED)
}

Is that the incorrect color code?

2

The RGB565 code for red is actually 0xF800.

3