A CFU is defined as a single, viable propagule that produces a single colony (a population of the cells visible to the naked eye) on an appropriate semisolid growth medium.
The colony counting problem can be easily solved by using the "CountThings By Camera" mobile app. You only need to take a photo, click to identify, and the whole process can be automatically completed, and the accuracy can also be adjusted.
You can download it at google play named "CountThings By Camera"