I know that when the ethernet cable flashes a certain color like orange or green I'm capable of 100/1000 mbps speed. But I have two laptops one being an Lenovo Ideapad p500 touch running on W8.1 and the other a Dell XPS 1640. When I plugged my ethernet cable to my Dell xps 1640 running on W7, the end of the ethernet cable connected to the modem would flash green. On the other hand when I plugged the ethernet cable into my Lenovo ideapad p500 touch it would flash orange. I used different ethernet cables and they would always flash green on my Dell and orange on my Lenovo. Oh and 1 important note my ethernet cable used to flash green on my Lenovo when I first purchased it. I added the Windows version just in case as I have experienced many problems on Windows 8 and 10.
Added (1). Btw my connection is 50/mbps but like I stated above, the ethernet cable used to flash green.