What does it mean code for TFT LCD rgb?
They are print and formatted print statements in the C language.

See any C reference on printf() such as this one for the format string. 

Presumably xprintf is the same as printf except it sends the characters to the LCD rather than stdout, and xputs() is likewise similar to puts().

\x12 and \x13 are the escape sequences for fairly rarely used control characters DC2 and DC2  (^R and ^S) with some unknown (to me) meaning, most likely to do with formatting on the display. Each of those represents a single byte.