Create and save multi-colored Brushes.
Rainbow Strokes and Brushes in Illustrator. In this tutorial you'll learn a quick way to make and save a multi-colored Brush that can be used as a stroke and can be customized using Illustrator's tools.
This is a great size to use for a Facebook banner
Create your document, any size is fine, let’s do a banner size of 1700 x 620 px, RGB color and a resolution of 72. Decide ahead of time how many colors you want to use for your Brush, for this example I'm going to use four colors. Make sure your Stroke is off.
Make a Square
For four colors we need to make four squares. Start creating the first square. Grab your rectangle tool and double click on the Art Board to bring up the Rectangle Options menu and type in 50 px for Height and Width to create a 50 x 50 px square.
Make sure your square is Selected before going to Effect
Grab your Selection tool, (the shortcut key is the v key) go to Effect click on it, then go to Distort & Transform from the drop down menu. Then select Transform to bring up it’s pop up Menu.
Use the settings in the image above to get these results.
Make sure Preview is on to see your changes. Type in the number of Copies you want. I put three to get four squares, including the original square. Since the square is 50 px, type 50 px in Move Vertical option and click OK. Now you have what looks like a straight up and down rectangle, it’s really four squares tight up against one another. When you Select this ‘rectangle’ only the top square will look selected. We’ll need to separate these squares by Expanding and Ungrouping them in order to color them.