the website has a color chart that indicates whether a color is transparent,opaque or semitransparent. or you can draw a thick black line with a permanent marker and paint your paints over the line,if the line is obscured then the paint is opaque if it is still seen then they are transparent.the series is like their 'set' in regards to the price point of their pigments,the series A being the cheapest lot and F for their more/most expensive pigments such as their cobalt violet light.