I completed this in class to swap through the colors of the rainbow when the switch is on.

switchInteraction.py

import time
import board
import neopixel
from digitalio import DigitalInOut, Direction, Pull

switch = DigitalInOut(board.D3)
switch.direction = Direction.INPUT
switch.pull = Pull.UP

pixel_pin = board.D2
num_pixels = 4
 
pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=0.3, auto_write=False)
 
RED = (255, 0, 0)
ORANGE = (255, 100, 0)
YELLOW = (255, 150, 0)
GREEN = (0, 255, 0)
CYAN = (0, 255, 255)
BLUE = (0, 0, 255)
PURPLE = (180, 0, 255)
PINK = (255, 100, 100)
WHITE = (255, 255, 255)
OFF = (0, 0, 0)

colors = [RED, ORANGE, YELLOW, GREEN, CYAN, BLUE, PURPLE, PINK, WHITE]
now = 0

while True:
    print(switch.value)
    if (switch.value == True):    #detect the button press
        now = now + 1 
        if (now >= 9): #9 colors in the list
            now = 0
        pixels.fill(colors[now])
        pixels.show()
    time.sleep(0.12)  # debounce delay