Hi azvmax,

The antenna wire is sold in 1100 mm lengths as some FM receivers require 1000mm and some require 1100mm's. Your R149DP requires 1000mm's. It is always best to stay with the original length of your receivers wire.
As for the impedence, the 100mm difference is nominal and will not affect the receiver at all.
The wire will not matter as long as you use stranded wire and not solid wire. Whether it is silver colored or copper colored will not matter, and it may be that the silver one is only colored that way is it is tinned on the ends.

I hope you find this information helpful. You can also reach our Futaba support technical team at 217-398-8970, or via fax at 217-398-7721.

Sincerely,
Krysta
Lead Futaba Customer Service and Programming Technician
Also you may want to check our Website at (http://www.futaba-rc.com)