If you want a specific colour to highlight a contact record of a field then you can include the colour in the tag such as shown here
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<td align="left" valign="top"><img src="images/contact_title.jpg" width="355" height="54" name="Image1"></td>
<td align="right" valign="top"><img src="images/contact_banner.jpg" width="470" height="54"></td>
One other area you can use colour is to set a contact as a "Primary" contact using a tick box on contact.html as shown below
<tr><td class=ContactBoldText><#label field=primarycontact label="Primary User" options=l></td>
<td class=ContactBoldText><#CHECKBOX field=primarycontact> <#label field=active options=l> <#CHECKBOX field=active></td></tr>
If you set it so that a tick in the box is always entered into the underlying databae as a T then the next part works really simply and can be applied to a host of other applications.
Then in Lookup.html add this to the standard selection
<td class=r<#LINE CYCLE=2>><#requestajax image="images/scontactd.gif" border=0><#field field=primarycontact noedit static test1=T val1="<b style='color:red;'>" > <#field field=company link=yes show=always></td>
Points to note: test1=T means if I find a T then display as style='color:red
If the primary contact is Red ?
Would the accounts be Green ?
Decision influencer be Orange ?
For support on issues such as this please contact firstname.lastname@example.org