Hi David, and
Ethernet cables come in all different shapes, lengths, and
colours. I wouldn't necessarily take colour as a good indicator of how fast a cable will operate.
Most ethernet cables are good up to 100Mbits/sec so I wuldn't have thought you would have much to worry about to be honest.
Does the cable have anything written on it?
---------- Post added at 18:56 ---------- Previous post was at 18:53 ----------
As an addition.....
It's quite normal to get a worse speed on wireless than on wired connections, the wireless signal is subject to interference (particularly from other wireless routers/devices) and that can have quite a pronounced affect on the speed/reliability.
Something else you might want to consider is how well secured the wireless device is.
If you haven't enabled WPA encryption as a minimum you could find some other bugger is using your wireless and that would probably cause it to run more slowly as they sucked up your bandwidth downloading pictures with a lot of pink in them.....if you get what I mean