Update Color.php

Author: Sergey

lib/Primal/Color/Color.php

@@ -4,14 +4,29 @@
 
 abstract class Color {
 
+	/**
+	 * @return HSVColor
+	 */
 	abstract function toHSV();
 
+	/**
+	 * @return HLSColor
+	 */
 	abstract function toHSL();
 
+	/**
+	 * @return RGBColor
+	 */
 	abstract function toRGB();
 
+	/**
+	 * @return CMYKColor
+	 */
 	abstract function toCMYK();
 
+	/**
+	 * @return string
+	 */
 	abstract function toCSS();
 }