(FORTUNE Magazine) – Bored with the look of your gray Apple Macintosh computer? David Siegel, 30, a Palo Alto, California, computer graphics and design consultant, will custom- paint your Mac to give it a new look. The two most popular colors: matte black and granite (up to $1,200 for painting a Mac SE). Pin stripes or copies of famous paintings, like surrealist Magritte's (see photo): at least $2,500. Owners of IBM PCs or compatibles need not apply. Siegel won't work on them. Says he: ''I guess I'm a Macintosh snob.'' Don't despair, all you non-Mac users. Ergo Computing, a Peabody, Massachusetts, manufacturer, has launched ''the brick,'' which is a $2,545 granite-patterned IBM compatible, and a $695 color monitor and keyboard. They provide consumers with at least one alternative to the usual beige of Ergo's product line.