About Color Images
When we say color images here, we mean:
1. Images that have information about color like (R, G, B) in each pixel. such a JPEGs, GIFs and BMPs.
2. Multi axis FITS image data displayed in color with each axis being represented by R, G, and B.
Each pixel of a FITS image has a value called a Count Value. Count Values usually represent the strength of electromagnetic waves received from astronomical objects. So, FITS data are fundamentally monochrome (gray scale).
Coloring done by [Color Mode] are for displaying purpose, and does not add color data such as (R, G, B) to the image itself. Also note that brightness calculated form the (R, G, B) of color images are not necessarily accurate.