This exercise is to demonstrate the effect of filtering out colours from images. We can do this with filters on the camera or in edit. I have used Lightroom. The image had to have the colours red, green, yellow and blue. A control grey card was also to be placed on the still life. As there was grey in the packaging this sufficed for the exercise. The original colour image is above and the neutral Lightroom conversion is next to it.
The images in the post below show the effect of filtering each colour out. Please read the observations under the below post.
This is an important exercise in learning how filtering can emphasise and add depth to a black and white conversion