USING COLORS WITH THE STANDARD GRAPHICS LIBRARY

Built-in colors. The simplest way to specify colors using standard draw is via a list of predefined colors. You can set the foreground color to blue with:

StdDraw.setPenColor(StdDraw.BLUE);

or clear the background to light gray with:

StdDraw.clear(StdDraw.LIGHT_GRAY);

The default foreground color is black and the default background color is white. Here is the complete list of predefined colors:

StdDraw.BLACK
StdDraw.BLUE
StdDraw.CYAN
StdDraw.DARK_GRAY
StdDraw.GRAY
StdDraw.GREEN
StdDraw.LIGHT_GRAY
StdDraw.MAGENTA
StdDraw.ORANGE
StdDraw.PINK
StdDraw.RED
StdDraw.WHITE
StdDraw.YELLOW
StdDraw.BOOK_BLUE
StdDraw.BOOK_LIGHT_BLUE
StdDraw.BOOK_RED

User-defined colors. The Java data type Color allows you to construct your own colors using RGB or HSB formats. (We'll introduce objects and the Color data type in Section 3.1.) For complete details, see the Java Color API. To access the Color data type, you need to include the following statement at the beginning of your Java program:

import java.awt.Color;

RGB format. RGB format specifies a color by three integer values between 0 and 255, representing the combination of red, green, and blue in the color. This format is commonly used in television screens, computer monitors, digital cameras, and web pages. (The primary color green is used instead of yellow because yellow phosphors are more expensive to produce.) You can create your own colors as follows:
```
StdDraw.setPenColor(new Color(255,   0,   0));   // red
StdDraw.setPenColor(new Color(  0, 255,   0));   // green
StdDraw.setPenColor(new Color(  0,   0, 255));   // blue
StdDraw.setPenColor(new Color(255, 255,   0));   // yellow
StdDraw.setPenColor(new Color(255, 255, 255));   // white
StdDraw.setPenColor(new Color(  0,   0,   0));   // black
StdDraw.setPenColor(new Color(100, 100, 100));   // gray
```
Note that if all three arguments are the same, you get a shade of gray. Web pages typically specify the colors in RGB format, but as a 24-bit hexadecimal integer. The Color.decode() method enables you to use this format.
```
StdDraw.setPenColor(Color.decode("#00ffff"));    // cyan
```
HSB format. HSB format specifies a color by three real values between 0.0 and 1.0, representing the hue, saturation, and brightness. The hue determines the color (from red to orange, yellow, green, blue, indigo, and violet). The brightness determines the intensity (from light to dark). The saturation determines the color depth (from dull to intense). This format roughly corresponding to the way in which the human eye perceives color. You can achieve a rainbow effect by varying the hue, while holding the saturation and brightness at 1.0. This can be useful for visualizing scientific data. For example, if you are plotting the movement of a particle over time, you might plot the particle in a different color at each time step.
```
for (int i = 0; i < 256; i++) {
    StdDraw.setPenColor(Color.getHSBColor(i / 256.0f, 1.0f, 1.0f));
    // plot something
}
```
The three arguments to Color.getHSBColor() must be of type float—this is why you need to use 1.0f instead of 1.0. The following code fragment generates a random color from the rainbow:
```
StdDraw.setPenColor(Color.getHSBColor((float) Math.random(), .8f, .8f));
```