You can specify solid colors using quoted text. The text should contain color's name or its RGB value. This means that both methods shown below result in a blue circle.
Personally, I like method 1 much better - it is much easier to read and understand. Code Shrew know about 147 different color names, so referring to colors by name doesn't mean you are limited to a small set of boring colors! The full list of available color names is included further down this page. The following code creates a fish colored... salmon:
To create a gradient just use a list of solid colors. For example, to create a circle gradually going from red to blue you can use the following code:
You can use an arbitrary number of colors. For example, the following code creates a rainbow frog: