I usually do the color correction after converting to B&W...
I use RawTherapee to process my RAWs, but I guess this would work with any other processor. When I decide to convert an image to B&W, I first lower the saturation to the minimum, and then play with the color balance and the RGB sliders. I am not interested in producing a "correct" color image, if the final result is going to be B&W, and quite often that intermediate color image ends with wild and surreal colors. But with this method, I can see how the changes affect to the final result.