A fastLED based chaser w 4 colours bouncing btwn each other

Four-band Bounce Chaser

#include <FastLED.h>
#define NUM_LEDS 12
#define PIN 6
CRGB leds[NUM_LEDS];

void setup() { 
  
FastLED.addLeds<NEOPIXEL, PIN>(leds, NUM_LEDS);

}

void loop() {
  //GREEN BAND
    for(int greenband = 0; greenband < (NUM_LEDS-1)/4+1/4; greenband++) { 
        leds[greenband] = CRGB::Green;       
        leds[greenband-1] = CRGB::Green;   
        leds[greenband+1] = CRGB::Green;  
//BLUE BAND
        leds[NUM_LEDS-1-greenband] = CRGB::Blue;    
        leds[NUM_LEDS-greenband] = CRGB::Blue;   
        leds[NUM_LEDS-2-greenband] = CRGB::Blue;         
//PINK BAND     
        leds[(NUM_LEDS-1)/2+1/2-greenband] = CRGB::Salmon;
        leds[(NUM_LEDS-1)/2+3/2-greenband] = CRGB::Salmon;
        leds[(NUM_LEDS-1)/2-1/2-greenband] = CRGB::Salmon;
//ORANGE BAND
        leds[(NUM_LEDS-1)/2+1/2+greenband] = CRGB::Orange;
        leds[(NUM_LEDS-1)/2+3/2+greenband] = CRGB::Orange;
        leds[(NUM_LEDS-1)/2-1/2+greenband] = CRGB::Orange;
        
        FastLED.show();
        delay(400);
        leds[greenband-1] = CRGB::Black;       
        leds[NUM_LEDS-greenband] = CRGB::Black; 
        leds[(NUM_LEDS-1)/2+3/2-greenband] = CRGB::Black;
        leds[(NUM_LEDS-1)/2-1/2+greenband] = CRGB::Black;   
}

        
 //COMING BACK
    for(int greenband = (NUM_LEDS-1)/4+1/4; greenband >= 0; greenband--) { 
        leds[greenband] = CRGB::Green;    
        leds[greenband-1] = CRGB::Green;   
        leds[greenband+1] = CRGB::Green;       
        leds[NUM_LEDS-1-greenband] = CRGB::Blue;    
        leds[NUM_LEDS-greenband] = CRGB::Blue;   
        leds[NUM_LEDS-2-greenband] = CRGB::Blue;
        leds[(NUM_LEDS-1)/2+1/2-greenband] = CRGB::Salmon;
        leds[(NUM_LEDS-1)/2+3/2-greenband] = CRGB::Salmon;
        leds[(NUM_LEDS-1)/2-1/2-greenband] = CRGB::Salmon;
        leds[(NUM_LEDS-1)/2+1/2+greenband] = CRGB::Orange;
        leds[(NUM_LEDS-1)/2+3/2+greenband] = CRGB::Orange;
        leds[(NUM_LEDS-1)/2-1/2+greenband] = CRGB::Orange;
              
        
        FastLED.show();
        delay(400);
        leds[greenband+1] = CRGB::Black;       
        leds[NUM_LEDS-2-greenband] = CRGB::Black;    
        leds[(NUM_LEDS-1)/2-1/2-greenband] = CRGB::Black;
        leds[(NUM_LEDS-1)/2+3/2+greenband] = CRGB::Black;   
}
 
}