Multi-language pertains to Color UI (#20972)

Marlin/Configuration_adv.h

 //
 // Specify additional languages for the UI. Default specified by LCD_LANGUAGE.
 //
-#if EITHER(DOGLCD, TOUCH_UI_FTDI_EVE)
+#if ANY(DOGLCD, TFT_COLOR_UI, TOUCH_UI_FTDI_EVE)
   //#define LCD_LANGUAGE_2 fr
   //#define LCD_LANGUAGE_3 de
   //#define LCD_LANGUAGE_4 es

Marlin/src/lcd/tft/tft_string.cpp

 
 #include "tft_string.h"
 #include "../fontutils.h"
+#include "../marlinui.h"
 
 //#define DEBUG_TFT_FONT
 #define DEBUG_OUT ENABLED(DEBUG_TFT_FONT)