local monitor = peripheral.find("monitor")
local chars = {
    "`", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "-", "=",
    "~", "!", "@", "#", "$", "%", "^", "&", "*", "?", ":", "_", "+"
}
local random_colors = {
    colors.red, colors.blue, colors.lime, colors.green
}

function drawText(x, y, text, color)
    monitor.setCursorPos(x, y)
    monitor.setBackgroundColor(color)
    monitor.write(text)
end

while true do
    for x = 1, 51 do
        for y = 1, 19 do
            drawText(x, y, chars[math.random(1, #chars)], random_colors[math.random(1, #random_colors)])
        end
    end
    os.sleep(1/24)
end