You can use a prism to split (or disperse) white light into a spectrum of colours: red, orange, yellow, green, blue, indigo and violet. Dispersed means that the colours are separated out.

orange-red lead chromate, bright yellow sodium chromate, brilliant chrome green (that's chrome(III) oxide), light blue chromium(II) chloride, and violet anhydrous chromium(III) chloride. The last of ...