how to simplify code
I have to say that I do not have any experience with the ws2812 led strip but basically it is used with the Adafruit_Neopixel library where you have the function pixel_obj.setPixelColor(pixel_number,pixel_obj.Color(R,G,B)
and the function pixel_obj.show().
Now you basically want to make the code in void loop() clean and there is a wide choice of possibilities and techniques to use. The simplest is not to do it, but if you want you can write a library to do it or write a function that takes the number of the pins and light 'em up (all with the same color), like this
void light_pixel(int pixels[],int Red,int Green,int Blue){
    for(int i=0;i&lt;NUMPIXELS;++i){
        pixel_obj.setPixelColor(pixels[i],pixel_obj.Color(Red,Green,Blue));
    }
    pixel_obj.show();
}
This works assuming you have declared pixel_obj in the outermost scope, and you will call the function like this:

#include &lt;Adafruit_NeoPixel.h&gt;
#define PIN //Whatever you pin is
#define NUMPIXELS //Thenumber of the pixels in your strip
Adafruit_NeoPixel pixel_obj = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
// You may have to modify the third parameter Rationale: You didn't 
// specified anything about your led strip
void setup(){
pixel_obj.begin();
pinMode(PIN, OUTPUT);
}
void light_pixel(int pixels[],int Red, int Green, int Blue){
for(int i=0;i&lt;NUMPIXELS &amp;&amp; pixels[I]!=-1 ;++i){
    pixel_obj.setPixelColor(pixels[i],pixel_obj.Color(Red,Green,Blue));
}
pixel_obj.show();
}
void loop(){
int my_pixels[NUMPIXELS]={1,3,5,7,-1}; // Using -1 as terminator
// Initialize the array . Disclaimer: this is not optimised and you might use
// new opearator or better pass the reference of a vector to the function so
// that you can modify the range of the vector and have a more concise function
light_pixel(my_pixels,255,255,255);
delay(1000);
light_pixel(my_pixels,0,0,0);
}


Then you can change the number of my_pixels with a smile array assignment
This function is just a sample to get the job done but I'd recommend you to study further the C/C++ programming language in general in order to write better code
Good Luck!