add a new FastColor type

src/Colors/ColorInput.cs

@@ -16,6 +16,8 @@ public sealed class ColorInput
         private readonly string _value0;
         private readonly int _value1;
         private readonly TinyColor _value2;
+        private readonly FastColor _value3;
+        private string _type;
 
         public ColorInput()
         {
@@ -27,6 +29,7 @@ private ColorInput(
             string value0 = default,
             int value1 = default,
             TinyColor value2 = default,
+            FastColor value3 = default,
             RGB rgb = default,
             RGBA rgba = default,
             HSL hsl = default,
@@ -38,51 +41,59 @@ private ColorInput(
             _value0 = value0;
             _value1 = value1;
             _value2 = value2;
+            _value3 = value3;
 
             if (rgb != default)
             {
                 R = rgb.R; 
                 G = rgb.G;
                 B = rgb.B;
+                _type = "rgb";
             }
             if (rgba != default)
             {
                 R = rgba.R;
                 G = rgba.G;
                 B = rgba.B;
                 A = rgba.A;
+                _type = "rgb";
             }
             if (hsl != default)
             {
                 H = hsl.H;
                 S = hsl.S;
                 L = hsl.L;
+                _type = "hsl";
             }
             if (hsla != default)
             {
                 H = hsla.H;
                 S = hsla.S;
                 L = hsla.L;
                 A = hsla.A;
+                _type = "hsl";
             }
             if (hsv != default)
             {
                 H = hsv.H;
                 S = hsv.S;
                 V = hsv.V;
+                _type = "hsv";
             }
             if (hsva != default)
             {
                 H = hsva.H;
                 S = hsva.S;
                 V = hsva.V;
                 A = hsva.A;
+                _type = "hsv";
             }
         }
 
         public static implicit operator ColorInput(string value) => new(0, value0: value);
         public static implicit operator ColorInput(int value) => new(1, value1: value);
         public static implicit operator ColorInput(TinyColor value) => new(2, value2: value);
+        public static implicit operator ColorInput(FastColor value) => new(3, value3: value);
         public static implicit operator ColorInput(RGB value) => new(-1, rgb: value);
         public static implicit operator ColorInput(RGBA value) => new(-1, rgba: value);
         public static implicit operator ColorInput(HSL value) => new(-1, hsl: value);
@@ -109,6 +120,8 @@ private ColorInput(
 
         public bool IsColor => _index == 2;
 
+        public bool IsFastColor => _index == 3;
+
         public string AsString =>
             _index == 0 ?
                 _value0 :
@@ -124,6 +137,16 @@ private ColorInput(
                 _value2 : 
                 throw new InvalidOperationException();
 
+        public FastColor AsFastColor =>
+            _index == 3 ?
+                _value3 :
+                throw new InvalidOperationException();
+
+        public bool Is(string type)
+        {
+            return type == _type;
+        }
+
         public override string ToString()
         {
             return _index switch