If the the saw is 220 volt then it`s best if your extension has a red and black and green. There is no neutral wire in that situation. It isn`t always possible to find stranded wire in those color codes, you may only be able to find black, white, and green. In that case both white and black are live conductors and green is ground (always, no exceptions on that color).
There are cases in house wiring where both white and black wires are live such as when the power feed to a light goes to the light receptacle first and then to a switch. The power goes from the light to the switch and comes back to the light also hot when the switch is turned on. Some inspectors I`ve dealt with like to see the white wire wrapped at the ends with either black or red electrical tape so that anyone looking at it will realize that it is not a neutral wire. You could do the same if necessary with your extension cord if it`s 220 and you can`t find red, black, and green in a flex cord.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.