From the User Manual - "2 Internet LED A solid light indicates connection on the Internet port. This LED blinks during data transmission."
The color information isn't given however is mostly an indication of link speed possibly between the router and ISP modem. Usually if the link speed is 100 to 1000Mb, it should be blinking green. Amber could mean 10Mb connection speed or there is a problem with the connection and the router has not been able to establish a correct connection to the ISP modem.
Are you getting Internet correctly using the 601?