Update the hex value for DarkSeaGreen color

Update the hex value for DarkSeaGreen color to 0xFF8FBC8F.

Based on W3 definition, the hex value for DarkSeaGreen color needs to be fixed:
https://www.w3.org/wiki/CSS/Properties/color/keywords

Fix issue: https://github.com/SixLabors/ImageSharp/issues/1015

src/ImageSharp/Color/Color.NamedColors.cs

@@ -174,9 +174,9 @@ namespace SixLabors.ImageSharp
         public static readonly Color DarkSalmon = FromRgba(233, 150, 122, 255);
 
         /// <summary>
-        /// Represents a <see paramref="Color"/> matching the W3C definition that has an hex value of #8FBC8B.
+        /// Represents a <see paramref="Color"/> matching the W3C definition that has an hex value of #8FBC8F.
         /// </summary>
-        public static readonly Color DarkSeaGreen = FromRgba(143, 188, 139, 255);
+        public static readonly Color DarkSeaGreen = FromRgba(143, 188, 143, 255);
 
         /// <summary>
         /// Represents a <see paramref="Color"/> matching the W3C definition that has an hex value of #483D8B.
@@ -718,4 +718,4 @@ namespace SixLabors.ImageSharp
         /// </summary>
         public static readonly Color YellowGreen = FromRgba(154, 205, 50, 255);
     }
-}
+}