Mandelbrot is a very simple to use OS X application that will allow you to easily generate gorgeous patterns using your Mac.
The Mandelbrot image generator uses a very simple formula to generate very complex patterns. You then choose what colors to use to draw the image
The histogram view shows you how many pixels of the image are of the colour defined above. The larger the height of the line used for that colour the more pixels will be coloured using that colour.
By noting the various peaks and troughs in the histogram and then adding or dragging colours to them you can colour the image.
NOTE: Mandelbrot can only be purchased via the Mac App Store (the buy link redirects you to its App Store page). To purchase/download applications via the App Store an Apple account is required.