Colour photometry as a simple alternative to spectra was introduced with the development of filtered photoelectric photometry in the 1950s. It is cruder in some ways and relies heavily upon empirical relationships. However, it is quicker and simpler than spectra and can reach much fainter magnitudes. This presentation initially explains what it is and how it has been used, with a variety of practical examples. It then discusses observational possibilities in a range of astrophysical aspects of stars which show evolutionary or other changes in their light and colour curves.