Ok, since I'm basically a noob in OS stuff, I spent some quality time in exploring how systemd works.
For those who might have a similar issue:
in /etc/systemd/system/hyperion.service, I added the following line to the [Service] section:
ExecStartPost=/bin/sh -c 'sleep 1 && hyperion-remote -u 1.0 -m 1.0 -g "2.0 2.0 2.0" -t "0.0 0.0 0.0" -R "255 0 0" -G "0 225 0" -B "0 0 205" -Z "255 110 70"'
Of course, the end part of the above command should be your desired settings.
The easiest way to grab them is to SSH through HyperCon, open the SSH log and just copy paste it.
I couldn't managed to make it run without the 'sleep X' part but it doesn't really make a difference since the startup animation runs during that time.