How do you score salmon and trout egg colour?

As part of my project I need to score brown and sea trout egg colour by eye and my friend has to do the same with salmon eggs. We are going to compare the shades electronically using imageJ however we also need to do a scoring by eye. Does anyone know of a method of scoring the eggs by eye or of a colour chart for salmon and trout eggs similar to that of the Salmofan but for eggs not flesh.