I have two fit-statUSB in one USB hub and adresses them via the
oneliner

sudo stty -F /dev/ttyACM0 115200 raw -echo -echoe -echok -echoctl -echoke ; echo "#E1D200" > /dev/ttyACM0

But I am not getting fast color changes and sometimes #FF0000 turns the usb GREEN and not RED !? Is there any "reset" command one can send to the stick so it behaves correctly ?

I found that sending "F0" to it makes it shift colors fast but the yellow color is .. not really yellow - it looks like green and you can clearly see the top of the USB is green and the bottom half red - is this normal ? (se picture where i used screen /dev/ttyACM0, then pressed H and then #FFFF00 )

The usage instructions for the fit-statUSB can be found at:
https://fit-pc.com/wiki/index.php?title=Fit-statUSB

As for resetting the configuration, setting a simple color should override previous configuration.

If the color behavior seems strange or malfunction, you may return the product.