Astronomers prefer to express star colors in terms of a difference in magnitudes, rather than a ratio of fluxes. Therefore, going back to blue Bellatrix we have a color index equal to
Os astrónomos prefiren expresar as cores das estrelas en termos de diferenzas de magnitudes no canto de relacións de fluxos. Polo tanto, volvendo á azul Bellatrix, temos un índice de cor igual a