The paint used in egg tempera, is ‘million year old’ stone, finely ground into powder and suspended in an egg/water emulsion.
The sandy particles settle on the flat surface, finding their own rest and natural condition. We use ground stone from all around the world, minerals, metals and oxides, that each has their own integrity and behavior as they dry.
Old iconographers used a limited pallet of earth pigments for Painting Egg Tempera. The various schools filled with icon painters jumped for joy when a traveling merchant would stroll into town. A bag a new earth pigments would be like amazon arriving at the door. They may have brought earth pigments from far way. In our world, we go to a store and purchase more than we need. We often buy earth pigments, colors we want to try but discover they are useless. I suggest you begin with a few colors, perhaps 12 earth colors. Choose pigments you find easy to work with and build on them. My book Icon Painting Technique, A Meditative Guide to Painting with Earth Pigments gives you an overview on the icon painting process and can help you start painting your first icons.