[css-backgrounds-4] Added parentheses to clarify border-color syntax

as suggested by @simevidas in #1172

Author: LeaVerou

css-backgrounds-4/Overview.bs

@@ -196,7 +196,7 @@ Painting Area: the 'background-clip' property</h3>
 	    <td><dfn id="border-color">border-color</dfn>
 	  <tr>
 	    <th><a href="#values">Value</a>:
-	    <td><<color>>{1,4}#
+	    <td>(<<color>>{1,4})#
 	  <tr>
 	    <th>Initial:
 	    <td>(see individual properties)
@@ -222,11 +222,11 @@ Painting Area: the 'background-clip' property</h3>
 
 	<p>These properties set the foreground color of the border specified
 	by the <span class=property>border-style</span> properties.
-	If a list of values is provided, the border is split into equal width bands of each color 
+	If a list of values is provided, the border is split into equal width bands of each color
 	along the direction of the side the border is applied on (i.e. split horizontally on left and right borders and vertically on top and bottom borders),
 	starting outwards.
 
-	<p>When interpolating between borders with the same number of colors, interpolation is performed individually per color band as <a href="https://www.w3.org/TR/css3-transitions/#animtype-color">color</a>. 
+	<p>When interpolating between borders with the same number of colors, interpolation is performed individually per color band as <a href="https://www.w3.org/TR/css3-transitions/#animtype-color">color</a>.
 		Interpolation between borders with different numbers of colors is discrete.
 
 	<p>'Border-color' is a shorthand for the
@@ -237,14 +237,14 @@ Painting Area: the 'background-clip' property</h3>
 
 	<div class="example">
 		Using multiple colors for each side:
-		
+
 		<pre>
 			border: 30px solid;
 			border-color: skyblue orange yellowgreen indianred, black yellow;
 		</pre>
 
 		Sample rendering:
-		
+
 		<img src="images/multicolor-border.png" alt="">
 
 		The same border colors with 'border-style: dotted':