IMO, from a Javascript point of view, everything works well as you programmed the script to function, since it changes to the colors that you desire...
Well, nevertheless, I get your point, so I programmed a little bit of code that can help you:
First of all, copy/paste this:
<script>
function conflict(){
if (document.bgColor==document.fgColor){
document.bgColor="white" <!--Here goes the color you want if there's a conflict-->
}
}
</script>
Afterwards, insert the function in the onchange event in the select box sfter the part that makes the foreground to change to the desired color after a ; like in the example below:
After that, look in the "black" option and do that in every onclick event after the document.bgColor function like what I did below in the "black" option:
<select onChange=document.fgColor=this.options[this.selectedIndex].value;conflict()>
<option value="black" selected>black</option>
<option value="silver">silver</option>
<option value="gray">gray</option>
<option value="white">white</option>
<option value="maroon">maroon</option>
<option value="red">red</option>
<option value="purple">purple</option>
<option value="fuchsia">fuchsia</option>
<option value="green">green</option>
<option value="lime">lime</option>
<option value="olive">olive</option>
<option value="yellow">yellow</option>
<option value="navy">navy</option>
<option value="blue">blue</option>
<option value="teal">teal</option>
<option value="aqua">aqua</option>
</select></form><br /><br />
<CENTER><TABLE COLS=6 BGCOLOR="#0099FF" WIDTH=50% BORDER=1 CELLPADDING=0 CELSPACING=0
BORDERCOLORDARK=#999999 BORDERCOLORLIGHT=#FFFFFF>
<TD><input type="radio" name="rRadio" value="black" onClick=document.bgColor="black";conflict()>black
<TD><input type="radio" name="rRadio" value="silver" onClick="document.bgColor='silver'">silver
<TD><input type="radio" name="rRadio" value="gray" onClick="document.bgColor='gray'">gray
<TD><input type="radio" name="rRadio" value="white" onClick="document.bgColor='white'">white
<TR>
<TD BGCOLOR=black onClick="document.fgColor='black'">
<TD BGCOLOR=silver onClick="document.fgColor='silver'">
<TD BGCOLOR=gray onClick="document.fgColor='gray'">
<TD BGCOLOR=white onClick="document.fgColor='white'"></TR>
<TR>
<TD><input type="radio" name="rRadio" value="maroon" onClick="document.bgColor='maroon'">maroon
<TD><input type="radio" name="rRadio" value="red" onClick="document.bgColor='red'">red
<TD><input type="radio" name="rRadio" value="purple" onClick="document.bgColor='purple'">purple
<TD><input type="radio" name="rRadio" value="fuchsia" onClick="document.bgColor='fuchsia'">fuchsia</TR>
<TR>
<TD BGCOLOR=maroon onClick="document.fgColor='maroon'">
<TD BGCOLOR=red onClick="document.fgColor='red'">
<TD BGCOLOR=purple onClick="document.fgColor='purple'">
<TD BGCOLOR=fuchsia onClick="document.fgColor='fuchsia'"></TR>
<TR>
<TD><input type="radio" name="rRadio" value="green" onClick="document.bgColor='green'">green
<TD><input type="radio" name="rRadio" value="lime" onClick="document.bgColor='lime'">lime
<TD><input type="radio" name="rRadio" value="olive" onClick="document.bgColor='olive'">olive
<TD><input type="radio" name="rRadio" value="yellow" onClick="document.bgColor='yellow'">yellow</TR>
<TR>
<TD BGCOLOR=green onClick="document.fgColor='green'">
<TD BGCOLOR=lime onClick="document.fgColor='lime'">
<TD BGCOLOR=olive onClick="document.fgColor='olive'">
<TD BGCOLOR=yellow onClick="document.fgColor='yellow'"></TR>
<TR>
<TD><input type="radio" name="rRadio" value="navy" onClick=document.bgColor="navy";conflict()>navy
<TD><input type="radio" name="rRadio" value="blue" onClick="document.bgColor='blue'">blue
<TD><input type="radio" name="rRadio" value="teal" onClick="document.bgColor='teal'">teal
<TD><input type="radio" name="rRadio" value="aqua" onClick="document.bgColor='aqua'">aqua</TR>
<TR>
<TD BGCOLOR=navy onClick="document.fgColor='navy'">
<TD BGCOLOR=blue onClick="document.fgColor='blue'">
<TD BGCOLOR=teal onClick="document.fgColor='teal'">
<TD BGCOLOR=aqua onClick="document.fgColor='aqua'"></TR>
</TABLE>