GIMP Experts

I have several color figures that I would like to redo in a B&W or gray scale that still looks good.  I have reprint permission or they are public domain.  How do I change these from solid colors to distinctive patterns?

There appears to be some questions about this figure.

This last one, if I could select all the red and change the color.

Hell, I can't get anything done today.  My Internet is running about 10 kbps download.

Never mind, the book will be color.  It is a bit more expensive but looks better.