Final answer:
Brian is using a mnemonic, specifically the acronym 'ROY G. BIV,' to remember the sequence of the visible spectrum colors from red to violet.
Step-by-step explanation:
Brian is using a mnemonic to remember the colors of the visible spectrum: red, orange, yellow, green, blue, indigo, and violet. These colors represent different wavelengths of visible light, with red having the longest wavelength and violet the shortest. The acronym 'ROY G. BIV' is a mnemonic device that helps individuals recall the order of colors in the spectrum, which is important for topics related to the physics of light and color perception.