I recently purchases an Odroid C2 unit which I used for hosting some sites. This site, amongst others, runs on it. The unit sits in my livingroom behind the couch. The case is transparent and there was an annoying blue light which blinks ever second. At day time this is not a problem, but during the evening and nights this became a problem. Lucky I found an easy solution on the Odroid forum:
sudo -Hi
echo none >/sys/class/leds/blue\:heartbeat/trigger
By executing these commands on the terminal of the device the blinking will stop. It is removed at reboot however, so you should add the 2nd line to your /etc/rc.local file to have it set at boot time.