might be quicker to point out what you're doing right...
to make text blue (without using a stylesheet) you'd just need to mark up the text like so:
<font color="blue">This text is blue</font>
so, firstly you'll need a space between the last ' of the "class" definition and the start of the colour definition.
Then you need to close the font tag ">".
I dont know what "<Width=30%>" is supposed to be doing - that's not valid HTML. if you're trying to set the width of the cell then it needs to be in the TD tag.
You should close the font tag after the text that you want to be blue, not before it.
Mightnt be a bad idea to have a look at a html tutorial to get to grips with the basics.
and option what you've posted doesnt fix anything, since all the mistakes listed above are still valid in your post. this one has nothing to do with escaping quote marks i'm afraid.
The line should read:
echo "<td width='30%'><font class='text10bold' color='#0000FF'>".$query_data["CustName"]."</font></td></tr>";