Quantitative analyses of transparent prehistoric glasses from Britain, Ireland, and France have been obtained using energy-dispersive x-ray fluorescence (EDXRF) and electron-probe microanalysis. The analyses of blue, turquoise, green, brown, and purple glasses have indicated the existence of compositional groupings which are determined by their major components, specifically the alkalies. The soda to potash ratios found in these glasses can probably be related to the nature of the raw materials used, e.g., plant ash or mineral. Transparent turquoise glass of the 9th-7th centuries BC later Bronze Age date in particular has been found to contain high potash contents, and the compositions discussed here are some of the first to be reported for European glass of the period. They were possibly made in Europe. For cobalt blue glass, the most commonly used color of glass in prehistoric Europe, further compositional groupings are apparent. It is possible to relate these groupings both to the typology of the blue artifacts and probably also to the sources of the mineral colorant employed, such as erythrite or cobaltite. A selection of highly colored glasses are discussed here. Consideration is given to the relative merits of using x-ray fluorescence and electron-probe microanalysis for glass analysis.