add skeleton for Color type

src/ImageSharp/Color.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Numerics;
+
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp
+{
+    public struct Color
+    {
+        private Rgba64 data;
+
+        public Color(Rgba64 pixel)
+        {
+            this.data = pixel;
+        }
+
+        public Color(Rgba32 pixel)
+        {
+            this.data = default;
+            this.data.FromRgba32(pixel);
+        }
+
+        public Color(Vector4 vector)
+        {
+            this.data = default;
+            this.data.FromVector4(vector);
+        }
+
+        public static Color FromRgba(byte r, byte g, byte b, byte a) => new Color(new Rgba32(r, g, b, a));
+        public static Color FromRgba(ushort r, ushort g, ushort b, ushort a) => new Color(new Rgba64(r, g, b, a));
+        
+        public TPixel ToPixel<TPixel>()
+            where TPixel : struct, IPixel<TPixel>
+        {
+            TPixel pixel = default;
+            pixel.FromRgba64(this.data);
+            return pixel;
+        }
+    }
+}

src/ImageSharp/PixelFormats/PixelImplementations/Rgba64.cs

@@ -54,6 +54,21 @@ namespace SixLabors.ImageSharp.PixelFormats
             this.A = a;
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Rgba64"/> struct.
+        /// </summary>
+        /// <param name="r">The red component.</param>
+        /// <param name="g">The green component.</param>
+        /// <param name="b">The blue component.</param>
+        /// <param name="a">The alpha component.</param>
+        public Rgba64(byte r, byte g, byte b, byte a)
+        {
+            this.R = r;
+            this.G = g;
+            this.B = b;
+            this.A = a;
+        }
+
         /// <summary>
         /// Gets or sets the RGB components of this struct as <see cref="Rgb48"/>
         /// </summary>

tests/ImageSharp.Benchmarks/Codecs/GetSetPixel.cs

@@ -10,11 +10,11 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs
     public class GetSetPixel : BenchmarkBase
     {
         [Benchmark(Baseline = true, Description = "System.Drawing GetSet pixel")]
-        public Color ResizeSystemDrawing()
+        public System.Drawing.Color ResizeSystemDrawing()
         {
             using (var source = new Bitmap(400, 400))
             {
-                source.SetPixel(200, 200, Color.White);
+                source.SetPixel(200, 200, System.Drawing.Color.White);
                 return source.GetPixel(200, 200);
             }
         }

tests/ImageSharp.Benchmarks/Drawing/DrawBeziers.cs

@@ -23,7 +23,7 @@ namespace SixLabors.ImageSharp.Benchmarks
                 graphics.InterpolationMode = InterpolationMode.Default;
                 graphics.SmoothingMode = SmoothingMode.AntiAlias;
 
-                using (var pen = new Pen(Color.HotPink, 10))
+                using (var pen = new Pen(System.Drawing.Color.HotPink, 10))
                 {
                     graphics.DrawBeziers(pen, new[] {
                         new PointF(10, 500),

tests/ImageSharp.Benchmarks/Drawing/DrawLines.cs

@@ -24,7 +24,7 @@ namespace SixLabors.ImageSharp.Benchmarks
                 graphics.InterpolationMode = InterpolationMode.Default;
                 graphics.SmoothingMode = SmoothingMode.AntiAlias;
 
-                using (var pen = new Pen(Color.HotPink, 10))
+                using (var pen = new Pen(System.Drawing.Color.HotPink, 10))
                 {
                     graphics.DrawLines(pen, new[] {
                         new PointF(10, 10),

tests/ImageSharp.Benchmarks/Drawing/DrawPolygon.cs

@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Benchmarks
             {
                 graphics.InterpolationMode = InterpolationMode.Default;
                 graphics.SmoothingMode = SmoothingMode.AntiAlias;
-                using (var pen = new Pen(Color.HotPink, 10))
+                using (var pen = new Pen(System.Drawing.Color.HotPink, 10))
                 {
                     graphics.DrawPolygon(pen, new[] {
                         new PointF(10, 10),

tests/ImageSharp.Benchmarks/Drawing/DrawTextOutline.cs

@@ -27,7 +27,7 @@ namespace SixLabors.ImageSharp.Benchmarks
             {
                 graphics.InterpolationMode = InterpolationMode.Default;
                 graphics.SmoothingMode = SmoothingMode.AntiAlias;
-                using (var pen = new Pen(Color.HotPink, 10))
+                using (var pen = new Pen(System.Drawing.Color.HotPink, 10))
                 using (var font = new Font("Arial", 12, GraphicsUnit.Point))
                 using (var gp = new GraphicsPath())
                 {

tests/ImageSharp.Benchmarks/Drawing/FillWithPattern.cs

@@ -24,7 +24,7 @@ namespace SixLabors.ImageSharp.Benchmarks
             {
                 graphics.SmoothingMode = SmoothingMode.AntiAlias;
 
-                using (var brush = new HatchBrush(HatchStyle.BackwardDiagonal, Color.HotPink))
+                using (var brush = new HatchBrush(HatchStyle.BackwardDiagonal, System.Drawing.Color.HotPink))
                 {
                     graphics.FillRectangle(brush, new Rectangle(0, 0, 800, 800)); // can't find a way to flood fill with a brush
                 }

tests/ImageSharp.Tests/ColorTests.cs

@@ -0,0 +1,10 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Tests
+{
+    public class ColorTests
+    {
+        
+    }
+}