Invert colors, change to grayscale as a toogle

I want to toogle my screen colors (for example with keyboard shortcut) between normal and inverted+grayscale. xcalib -i -a does what I need to invert them, but does not seem to be capable for making them grayscale. The answer from suggests that I need to change the configuration file, but how to make it as toggle?

The ideal behaviour for color changes should look like:

Bonus: To get it even more useful I would like to apply these color changes only for specific window (web browser, word processor, etc).

Know someone who can answer? Share a link to this question via email, Twitter, or Facebook.