How to Highlight the Author Comments in Blogger?

1. Login to your Blogger Dashboard
2. Select Design Section
3. Choose Edit HTML tab
4. Check Expand Widgets (i.e., Tick Expand Widgets check box)
5. Find ]]></b:skin> Tag in Your template
6. Add Bellow code Before it 

.comment-body-author {
    background: #CEF6E3;
    border: 2px solid #FA5858;
    padding: 5px;
}

7. Now Save your template

Third Step:- Adding Xml Code
Add this code very carefully

1. Find the following section of code in your template
2. I am not sure the code exactly like bellow
   But <data:comment.body/> tag must present in code
   So Find <data:comment.body/> tag and then select entire code like bellow

   <dd class='comment-body'>
   <b:if cond='data:comment.isDeleted'>
   <span class='deleted-comment'><data:comment.body/></span>
   <b:else/>
   <p><data:comment.body/></p>
   </b:if>
   </dd>

3. After finding code successfully then Add Bellow code Before it

   <b:if cond='data:comment.author == data:post.author'>
   <dd class='comment-body-author'>
   <p><data:comment.body/></p>
   </dd>
   <b:else/>

4. and Add bellow code After it

   </b:if>

5. After adding Above two codes then Save your template and check your Comments

Your final change in code like bellow

<b:if cond='data:comment.author == data:post.author'>
<dd class='comment-body-author'>
<p><data:comment.body/></p>
</dd>
<b:else/>


<dd class='comment-body'>
<b:if cond='data:comment.isDeleted'>
<span class='deleted-comment'>
<data:comment.body/></span>
<b:else/>
<p><data:comment.body/></p>
</b:if>
</dd>


</b:if>