The clock applet now has three parameters; the background color (bgcolor), the main foreground color (the hands and dial) (fgcolor1) and the secondary foreground color (the seconds hand and numbers) (fgcolor2). These three parameters are hexadecimal RGB numbers (like the ones used for the body bgcolor tag in HTML). For example:
<applet code="Clock.class" width=170 height=150>
<param name=bgcolor value="000000">
<param name=fgcolor1 value="ff0000">
<param name=fgcolor2 value="ff00ff">
would give you a black background, a red dial and hands, and purple numbers.
For those who don't convert to hexadecimal easily, here are some common values: