General :: Remove Background Layer Of Djvu File?

I've downloaded some files from the Internet Archive. They come in different file formats and most of the time I use pdf. However, sometimes the scans are saves in colour instead of b/w. This makes it difficult/impossible to read on a dedicated ebook reader. In that case I downloaded the djvu files as on the PC you can select which layer (color, bw,fore,back) one would like to see. Selecting the bw gives excellent results. However, the ebook reader does not has this option.

The question is, how can I remove /extract a layer from the djvu file and save only this layer.

So far I've tried the following two approaches:

1) select bw in the djvu viewer on the PC and printed to postscript file. Followed by a ps2pdf conversion. This works, but generates a fairly large pdf file. Sure, I can again upload it to any2djvu but it just seems to much manual work for each file.

2) I tried the shared annotation feature and said (mode bw). This works on the PC as desired but is ignored on the ebook reader as the other layers are still present.