[css-color-5] Improve device-cmyk grammar, #9445

Author: svgeesus

css-color-5/Overview.bs

@@ -2316,18 +2316,21 @@ or any other color or monochrome output device which has been characterized.
 		The ''device-cmyk()'' function allows authors to specify a color in this way:
 
 		<pre class='prod'>
-			<dfn>device-cmyk()</dfn> = device-cmyk( <<cmyk-component>>{4} [ / <<alpha-value>> | ''none'' ]? )
+			<dfn>device-cmyk()</dfn> = <<legacy-device-cmyk-syntax>> | <<modern-device-cmyk-syntax>>
+			<dfn>&lt;legacy-device-cmyk-syntax></dfn> = device-cmyk( <<number>>#{4} ) 
+			<dfn>&lt;modern-device-cmyk-syntax></dfn> = device-cmyk( <<cmyk-component>>{4} [ / <<alpha-value>> | ''none'' ]? )
 			<dfn>&lt;cmyk-component></dfn> = <<number>> | <<percentage>> | ''none''
 		</pre>
 
 		The arguments of the ''device-cmyk()'' function specify the cyan, magenta, yellow, and black components, in order,
-		as a number between 0 and 1 or a percentage between 0% and 100%.
+		as a number between 0 and 1 
+		or, in the modern syntax, as a percentage between 0% and 100%.
 		These two usages are equivalent, and map to each other linearly.
 		Values less than 0 or 0%, or greater than 1 or 100%,
 		are not invalid;
 		instead, they are clamped to 0/0% or 1/100% at computed-value time.
 
-		The fifth argument specifies the alpha channel of the color.
+		In the modern syntax, the fifth argument specifies the alpha channel of the color.
 		It's interpreted identically to the fourth argument of the ''rgb()'' function.
 		If omitted, it defaults to ''100%''.