The original image is:
And the black white version becomes:
As you can see, the cyan colored cells disappear in the black & white version. How can I modify the original image so that the contrast is maintained in the black and white version?
Answer
After decomposing a coloured image to it’s RGB colors we often find a resulting gray-scale that suits our needs better that a gray scale based on brightness values alone:
Red: 
Green: 
Blue: 
With Gimp this can be done using Colors > Components > Decompose….
Attribution
Source : Link , Question Author : Gigili , Answer Author : Takkat