How To: Work with true color or multiband images in GRID
A true color image has three different bands of pixels. Each band represents a color component of the RGB (red-green-blue) color model. Usually each band will be eight bits per pixel. The whole image will then be 24 bits per pixel.
Use DESCRIBE to determine if the image is a multiband.
Use IMAGEGRID to convert the image to a grid stack and separate grids.
Make your changes to each individual grid.
Use MAKESTACK to convert the separate grids to a stack.
Use GRIDIMAGE to convert the stack back to an image.