All you need is a tri color led
eg [
www.sparkfun.com]
You connect each color to a IO pin. (doesn’t needs to be a PWM pin if your just wanting on and off)
Looks like this is mostly already in marlin,
See in configuration.h
// Support for an RGB LED using 3 separate pins with optional PWM
//#define RGB_LED
#if ENABLED(RGB_LED)
#define RGB_LED_R_PIN 34
#define RGB_LED_G_PIN 43
#define RGB_LED_B_PIN 35
#endif
then M150 - Set Status LED Color as R U B. Values 0-255.
But there is no code to change color related to temp. Someone would have to add this.