Color Bitmaps on Displayio

hello_bitmap.py

# SPDX-FileCopyrightText: Copyright (c) 2021 Randall Bohn (dexter)
#
# SPDX-License-Identifier: MIT
"""A first look at DisplayIO"""
import time
import board
import displayio
import vectorio

display = board.DISPLAY
splash = displayio.Group()
background_palette = displayio.Palette(3)
background_palette[0] = 0x336699
background_palette[1] = 0x990000
background = displayio.Bitmap(display.width, display.height, 3)
background_tg = displayio.TileGrid(background, pixel_shader=background_palette)
splash.append(background_tg)

display.show(splash)
print("bitmap fill")
sleeptime = 2
for _ in range(2):
    background.fill(0)
    time.sleep(sleeptime)
    background.fill(1)
    time.sleep(sleeptime)

print("palette update")
background.fill(2)
for _ in range(2):
    background_palette[2]=0x339933
    time.sleep(sleeptime)
    background_palette[2]=0x993333
    time.sleep(sleeptime)