Fade whole strip from one color to another

#include <FastLED.h>
#define LED_PIN     6                //CONFIGURE LED STRIP HERE
#define NUM_LEDS    164
#define BRIGHTNESS  100
#define LED_TYPE    WS2812B
#define COLOR_ORDER GRB
CRGB leds[NUM_LEDS];
#define UPDATES_PER_SECOND 100

//Previous value of RGB
int redPrevious, greenPrevious, bluePrevious = 0;

//Current value of RGB
float redCurrent, greenCurrent, blueCurrent = 0;

//Target value of RGB
int redTarget, greenTarget, blueTarget = 0;

int fade_delay = 5;
int steps = 50; //This is where you tell it how smooth of a transition you want it to be

void setup() {
  Serial.begin(9600);
  delay( 3000 ); // power-up safety delay
  FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip );
  }
void loop() { // Here is where you tell it what colours you want!

  FadeToColour(0, 0, 225); // blue
  FadeToColour(0, 225, 0); // green
  FadeToColour(255, 100, 0); // redish-orange
  FadeToColour(0, 225, 0); // green

}

void FadeToColour(int r, int g, int b) {
  redPrevious = redCurrent;
  greenPrevious = greenCurrent;
  bluePrevious = blueCurrent;

  redTarget = r;
  greenTarget = g;
  blueTarget = b;

  float redDelta = redTarget - redPrevious;
  redDelta = redDelta / steps;

  float greenDelta = greenTarget - greenPrevious;
  greenDelta = greenDelta / steps;

  float blueDelta = blueTarget - bluePrevious;
  blueDelta = blueDelta / steps;

  for (int j = 1; j < steps; j++) {
    redCurrent = redPrevious + (redDelta * j);
    greenCurrent = greenPrevious + (greenDelta * j);
    blueCurrent = bluePrevious + (blueDelta * j);
    fill_solid(redCurrent, greenCurrent, blueCurrent, leds);
    delay(fade_delay);  //Delay between steps
  }
  delay(1000); //Wait at peak colour before continuing
}

void fill_solid(int r, int g, int b, int lednum) {
  Serial.println(r);

  for(int x = 0; x < NUM_LEDS; x++){ //This tells it to affect the whole strip instead of indivual ones.
  leds[x] = CRGB(r,g,b);

  FastLED.show();
  }
}