Each grid has a light yellow
background when first displayed. As cells are selected colours cycle through red, yellow and blue (cyan).
The object is to determine the minimum cell selections to present a layer of red, then a layer of yellow and finally blue for each grid option offered (or at least be able to move from one layer to the next which is less restrictive).
Those acquainted with "Lights Switched"
will be aware of the ease to meet the 3x3 and 4x4 requirements of that problem. For those configurations here the situation may not be quite as easy, but how do you proceed with the other configurations?