+3 for the links.
-1 for the missing constructor !!
From C:\Users\David Prentice\Documents\Arduino\libraries\UTFT\examples\Arduino (AVR)\UTFT_Demo_800x480\UTFT_Demo_800x480.ino
// Remember to change the model parameter to suit your display module!
UTFT myGLCD(ITDB50,38,39,40,41);
You should use the appropriate constructor e.g.
UTFT myGLCD(CTE70,38,39,40,41);
From C:\Users\David Prentice\Documents\Arduino\libraries\UTFT\UTFT.h
#define SSD1963_480 12
#define SSD1963_800 13
...
#define SSD1963_800ALT 20
...
#define ITDB43 12 // SSD1963 (16bit) 480x272
#define ITDB50 13 // SSD1963 (16bit) 800x480
#define CTE50 13 // SSD1963 (16bit) 800x480
#define EHOUSE50 13 // SSD1963 (16bit) 800x480
...
#define CTE70 20 // SSD1963 (16bit) 800x480 Alternative Init
#define EHOUSE70 20 // SSD1963 (16bit) 800x480 Alternative Init
For some reason Mr Karlsen prefers to use gobbledygook "model names" which is fine if you have bought your screen from one of his preferred suppliers e.g. ColdTears.
Personally I am happier with a Controller name like SSD1963_800_7 but this is not my library.
Please paste your constructor statement.
Mirroring, wrong colours, wrong direction, ... are easy for me to fix. But only when I know which constructor you are using.
Panels vary. Which is why you can configure controllers to suit different colours, directions etc.
Forget about GUISlice until you have your screen working correctly.
David.