flexi-bot/docs/marlin/_gcode/M250.md

tag	title	brief	author	requires	group	codes	notes	parameters	examples
m0250	LCD Contrast	Set and/or get the LCD contrast.	thinkyhead	HAS_LCD_CONTRAST	lcd	M250	Requires an LCD controller with software-controlled contrast.	tag optional description values C true Contrast value tag type contrast int

Set and/or get the LCD contrast. The value is constrained based on the LCD.