Blue Green is cyan which is minus red.
The B+W filters for this are CC Filters Cyan (blue-green) 05, 10, 20, 40 on Page 23 of their filter manual PDF which you can download by clicking on the below link. (using right click and "save target as" might be best). It's 7MB.
40 takes out most red. 05 the least.
They are available in a 39 thread. See towards of end document for sizes.
http://www.schneiderkreuznach.com/pd...r_handbook.pdf