Question adjustable red line for rpm, with ws2812b leds and arduino

hi all need hel pon a project im working on ive got the basic code setup so i can addust what coulors are on which leds but im wanting to be able to use a pot to change the red lights for the redline on the rpm gauge


problem is im not that good at coding, so im asking for yuo help to finish this and then do a tut to let everyone know,

the program is simple..... ish

there aee ws2812b leds and i have the 5v and gnd connect to the arduino and the data pin to pin 4


now i now that i can add a pot to this on a analog.read pin but i dont know how to right the come for the pot to change the leds from blue to red and vis verser

heres a pic of my project so far..

this is my code i have so far, really want to get this working and i really need the help

kind regards

andy

Code:

#include <FastLED.h>

#define LED_PIN     4
#define NUM_LEDS    10
#define LED_TYPE    WS2812B
#define COLOR_ORDER GRB
#define BRIGHTNESS  64

CRGB leds[NUM_LEDS];

void setup() {
    delay(1000);
    LEDS.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS);
    FastLED.setBrightness(BRIGHTNESS);
} // setup ()

void loop() {         // 0 is the first led ie: 1 ...... so if 10 led itll be 0 to 9 on the crgb led num

  leds[0] = CRGB::Blue;
  leds[1] = CRGB::Blue;
  leds[2] = CRGB::Blue;
  leds[3] = CRGB::Blue;
  leds[4] = CRGB::Blue;
  leds[5] = CRGB::Blue;
  leds[6] = CRGB::Blue;
  leds[7] = CRGB::Red;
  leds[8] = CRGB::Red;
  leds[9] = CRGB::Red;

  FastLED.show();

} // loop ()

Hey guys

I've made a tutorial on how to do this in the diy peripherals called adjustable rpm leds

I figured out how to do this with my brother who is great a c++ as he is working with it a lot and Arduino ide is kind of like c++ so he made this possible go check it out

Kind regards

Andy