what app are you using? Menu Meters allows you to customize the colors and it has been ported for 10.11 which I can confirm works with 10.12 Sierra as well. https://www.reddit.com/r/apple/comments/3n7z5y/menumeters_was_ported_for_mac_os_x_el_capitan_1011/ http://member.ipmu.jp/yuji.tachikawa/MenuMetersElCapitan/
Just ran test with MenuMeters and getting a more accurate reading now. Not sure why 45.1 MB/s is showing for 336.87 Mb/s, but at least its in the ballpark now.
ah...I was unaware.
I did, however, find a work-around for the Menu Meters that according to this guy works. Might test it out on my MacBook tonight.