I was able to finish this in class, a continuation from the last gist.

rainBow.py

# Write your code here :-)
import time
import board
import neopixel

pixel_pin = board.D2   #the ring data is connected to this pin
num_pixels = 4        #number of leds pixels on the ring

pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=0.5, auto_write=False)

RED = (255, 0, 0) #RGB
YELLOW = (255, 150, 0)
GREEN = (0, 255, 0)
CYAN = (0, 255, 255)
BLUE = (0, 0, 255)
PURPLE = (180, 0, 255)
WHITE = (255, 255, 255)
OFF = (0, 0, 0)

myCOLORS = [RED, YELLOW, GREEN, CYAN, BLUE, PURPLE, WHITE, OFF]

while True:  
    for color_index in range(0, len(myCOLORS), 1):
        pixels[0] = myCOLORS[color_index]
        pixels.show()
        color_index = color_index + 1
        if (color_index >= 7):
            color_index = 0
        pixels[1] = myCOLORS[color_index]
        pixels.show()
        color_index = color_index + 1
        if (color_index >= 7):
            color_index = 0
        pixels[2] = myCOLORS[color_index]
        pixels.show()
        color_index = color_index + 1
        if (color_index >= 7):
            color_index = 0
        pixels[3] = myCOLORS[color_index]
        pixels.show()
        time.sleep(0.1)