Conceptually, I'd be inclined to have a method (call it 'acceptChanges') which could be invoked before you generate the HTML output.  But I don't think we have that yet.  And the downside is from an efficiency point of view, it would be an additional traversal of the document.
The XSLT in package org.docx4j.convert.out.html contains:
Using xml Syntax Highlighting
                                        /*element styles*/ .del
                                        {text-decoration:line-through;color:red;}
                                        
<xsl:choose>
                                                <xsl:when test="/w:document/w:settings/w:trackRevisions">
                                                  .ins {text-decoration:none;background:#c0ffc0;padding:1px;}
                                                
</xsl:when>
                                                <xsl:otherwise>
                                                  .ins {text-decoration:none;background:#c0ffc0;padding:1px;}
                                                
</xsl:otherwise>
                                        </xsl:choose>
  <xsl:template match="w:ins">
        <span class="ins">
                <xsl:apply-templates/>
        </span>
  </xsl:template>       
  <xsl:template match="w:del">
                <xsl:apply-templates/>
  </xsl:template>       
  <xsl:template match="w:delText">
        <span class="del">
                <xsl:apply-templates/>
        </span>
  </xsl:template>       
 Parsed in 0.002 seconds,  using 
GeSHi 1.0.8.4
 
  so an expdient approach would be to alter the CSS definitions, or change these templates.