Lighting, Light Fixtures, Ceiling and Exhaust Fans - Problems replacing ceiling light fixture

I went to replace an old ceiling light fixture, something i thought would be straight forward until i opened the box of the new fixture. Instead of the code white and black wire coming from the fixture, there is white, black and another wire that is sheathed in green and yellow. Is it possible that this green-yellow wire is the ground. Can a ground wire be made of something other than copper, because it appears to be aluminum. Also, the white and black wires also appear to be aluminum. Do i need special connectors to attach these to the white and black copper wire in the ceiling? Thanks for you advice.

the green w/ yellow atripe is the ground.

The wire you have may be tinned copper. Aluminum is quite soft. If you scrape the wire, is there copper under the surface of is it the same clear through. It is not unusual to have tinned wire on a light or such.

If this is aluminum, there are special methods to repair this. Do not attach it directly to the copper wire of your house.

new fixture? New to you?
New fixture, don't worry. Wire it the same as the old one.