Top-tone is adding White to the color. Under-tone is adding clear. Mass-tone is thick out of the tube. Transparent is clear, like colored glass crystal or Easter egg food coloring. Translucent is floating colloidal compounds of colored elements.
Milk is translucent.
Opaque is dense and light blocking, like a rock. This is the normal afternoon darkest shadow color combination of colors. Mornings would use a Brown and Ultramarine opposition. Thalo Blue and Cadmium Red opposition happens in the evening. Mix this opposite with this opposite color.