You can find the source code decay.java as attachement file of the third message.
Those labels can be modified as parameters for applet tag.

You need to modified the source code for the background color.

<applet width="600" height="340" codebase="/java/decay/" code="decay.class"><param value="reset" name="Reset" /><param value="start" name="Start" /><param value="time=" name="Time" /><param value="[u]decay time ?1[/u]" name="[b]tau1[/b]" /><param value="?2" name="[b]tau2[/b]" /><param value="?3" name="[b]tau3[/b]" /><param value="?4" name="[b]tau4[/b]" /></applet>