I am describing fungal colonies but I do not want to be ambiguous about the color description. Is there a standard code for colors? I know of color handbooks but those are not publicly available as they need to be purchased?
Andres Sanabria-Velazquez, there is a link to very similar question, please, take a look:
https://www.researchgate.net/post/Is_there_a_Software_App_Website_to_label_specific_colours
Each color can be represented by 3 numbers, for example, by the RGB numbers. Here, white is represented as (255, 255, 255), black is (0, 0, 0), and pure green is (0, 255, 0). Many image processing software programs will tell you the RGB numbers for a given color in a photo. Note, however, that color depends on illumination and sensor sensitivity, etc.
RGB does not help really because as written in the links above, it depends on the light-source and in any way it is device-dependent. If Your department has a bit of money You can buy a spectral photometer and simply measure the surface. Than You can store the reflectance or You can transform to CIE-Lab for instance and store these 3 values. These descriptions of colours are independent of light-source and device.
Visit www.color.bio. Here you can find colour name, Fungi name, RGB number etc.