This tip is very usefull for every blogger.If you like this follow the steps below.

1.Log in to your dashboard--> layout- -> Edit HTML

2.Click on "Expand Widget Templates"

3.Scroll down to where you see this:-

]]></b:skin>

4.Copy below code and put it before ]]></b:skin>

.comment-body-author {
background: #E6E6E6; /* Background color*/
color: #000; /* Text color*/
border-top: 1px dotted #223344;border-bottom: 1px dotted #223344;border-left: 1px dotted #223344;border-right: 1px dotted #223344;
margin:0;
padding:0 0 0 20px; /* Posotion*/
}

5.Now Scroll down to where you see this:-

<dl id='comments-block'>
<b:loop values='data:post.comments' var='comment'>
<dt class='comment-author' expr:id='"comment-" + data:comment.id'>
<a expr:name='"comment-" + data:comment.id'/>
<b:if cond='data:comment.authorUrl'>
<a expr:href='data:comment.authorUrl' rel='nofollow'><data:comment.author/></a>
<b:else/>
<data:comment.author/>
</b:if>
said...
</dt>

<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>

6.Replace above code with below code.

<dl id='comments-block'>
<b:loop values='data:post.comments' var='comment'>
<dt class='comment-author' expr:id='"comment-" + data:comment.id'>
<a expr:name='"comment-" + data:comment.id'/>
<b:if cond='data:comment.authorUrl'>
<a expr:href='data:comment.authorUrl' rel='nofollow'><data:comment.author/></a>
<b:else/>
<data:comment.author/>
</b:if>
said...
</dt>

<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>

7.Click on "Save Templates" and you are done.

Note : You can change "Background color" , "Text color" and "Posotion" of above codes.