In the digital world, when we want to talk about a color, precision is required. Saying "Hey, can you make that circle bluish-green?" will not do. Color, rather, is defined as a range of numbers. Let's start with the simplest case: black & white or grayscale. 0 means black, 255 means white. In between, every other number - 50, 87, 162, 209, and so on - is a shade of gray ranging from black to white.

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<em>Does 0-255 seem arbitrary to you?</em><br />

Color for a given shape needs to be stored in the computer's memory. This memory is just a long sequence of 0's and 1's (a whole bunch of on or off switches.) Each one of these switches is a bit, eight of them together is a byte. Imagine if we had eight bits (one byte) in sequence - how many ways can we configure these switches? The answer is (and doing a little <a href="http://en.wikipedia.org/wiki/Binary_number">research into binary numbers</a> will prove this point) 256 possibilities, or a range of numbers between 0 and 255. We will use eight bit color for our grayscale range and 24 bit for full color (eight bits for each of the red, green, and blue color components).

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By adding the <strong><a href="http://processing.org/reference/stroke_.html">stroke()</a></strong> and <strong><a href="http://processing.org/reference/fill_.html">fill()</a></strong> functions before something is drawn, we can set the color of any given shape. There is also the function <strong><a href="http://processing.org/reference/background_.html">background()</a></strong>, which sets a background color for the window. Here's an example.

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