Photoshop has a feature called Photomerge that you can use for this. First, when taking the pictures, make sure you have quite a bit of overlap between adjacent frames, like 30%. It also helps if there's good detail — open water and clear skies don't work well. Including some objects on the floor and ceiling might help, too.
Once you have the photos, open them all up in Photoshop, and File > Automate > Photomerge (down there at the bottom of the menu). Choose Cylindrical: objects in the room may have that 'panorama effect', but the wall will be mapped to a flat rectangle.
Once you have the merged photo, there are a number of ways you could select and mark areas of certain colors, but a lot of that depends on the particular image and colors.
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