I actually do not understand how the colors mix from red to yellow.

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import java.awt.*;
import javax.swing.*;

/**
* Class spectrum - write a description of the class here
*
* @author (your name)
* @version (a version number)
*/
public class spectrum extends JApplet
{
// instance variables - replace the example below with your own
private int x;
int width, height;
int N = 25; // the number of colors created
Color[] spectrum; // an array of elements, each of type Color
Color[] spectrum2; // another array

/**
* Called by the browser or applet viewer to inform this JApplet that it
* has been loaded into the system. It is always called before the first
* time that the start method is called.
*/
public void init()
{
// this is a workaround for a security conflict with some browsers
// including some versions of Netscape & Internet Explorer which do
// not allow access to the AWT system event queue which JApplets do
// on startup to check access. May not be necessary with your browser.
JRootPane rootPane = this.getRootPane();
rootPane.putClientProperty("defeatSystemEventQueueCheck", Boolean.TRUE);

// provide any initialisation necessary for your JApplet

width = getSize().width;
height = getSize().height;
setBackground( Color.black );

// Allocate the arrays; make them "N" elements long
spectrum = new Color[ N ];
spectrum2 = new Color[ N ];

// Generate the colors and store them in the arrays.
for ( int i = 1; i <= N; ++i ) {
// The three numbers passed to the Color() constructor
// are RGB components in the range [0,1].
// The casting to (float) is done so that the divisions will be
// done with floating point numbers, yielding fractional quotients.

// As i goes from 1 to N, this color goes from almost black to white.
spectrum[ i-1 ] = new Color( i/(float)N, i/(float)N, i/(float)N );

// As i goes from 1 to N, this color goes from almost pure blue to pure red.
spectrum2[ i-1 ] = new Color( i/(float)N, 0,(N-i)/(float)N );
}
}

/**
* Called by the browser or applet viewer to inform this JApplet that it
* should start its execution. It is called after the init method and
* each time the JApplet is revisited in a Web page.
*/
public void start()
{
// provide any code requred to run each time
// web page is visited
}

/**
* Called by the browser or applet viewer to inform this JApplet that
* it should stop its execution. It is called when the Web page that
* contains this JApplet has been replaced by another page, and also
* just before the JApplet is to be destroyed.
*/
public void stop()
{
// provide any code that needs to be run when page
// is replaced by another page or before JApplet is destroyed
}

/**
* Paint method for applet.
*
* @param g the Graphics object for this applet
*/
public void paint( Graphics g ) {

int step = 90 / N;
for ( int i = 0; i < N; ++i ) {
g.setColor( spectrum[ i ] );
g.fillArc( 0, 0, 2*width, 2*height, 90+i*step, step+1 );

g.setColor( spectrum2[ i ] );
g.fillArc( width/3, height/3, 4*width/3, 4*height/3,
90+i*step, step+1 );
}
}

/**
* Called by the browser or applet viewer to inform this JApplet that it
* is being reclaimed and that it should destroy any resources that it
* has allocated. The stop method will always be called before destroy.
*/
public void destroy()
{
// provide code to be run when JApplet is about to be destroyed.
}


/**
* Returns information about this applet.
* An applet should override this method to return a String containing
* information about the author, version, and copyright of the JApplet.
*
* @return a String representation of information about this JApplet
*/
public String getAppletInfo()
{
// provide information about the applet
return "Title: \nAuthor: \nA simple applet example description. ";
}


/**
* Returns parameter information about this JApplet.
* Returns information about the parameters than are understood by
this JApplet.
* An applet should override this method to return an array of Strings
* describing these parameters.
* Each element of the array should be a set of three Strings containing
* the name, the type, and a description.
*
* @return a String[] representation of parameter information
about this JApplet
*/
public String[][] getParameterInfo()
{
// provide parameter information about the applet
String paramInfo[][] = {
{"firstParameter", "1-10", "description of first parameter"},
{"status", "boolean", "description of second parameter"},
{"images", "url", "description of third parameter"}
};
return paramInfo;
}
}




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