color writer

ACadSharp/Color.cs

@@ -1,4 +1,5 @@
-using System;
+using CSUtilities.Converters;
+using System;
 
 namespace ACadSharp
 {
@@ -323,6 +324,21 @@ public bool IsTrueColor
 			}
 		}
 
+		/// <summary>
+		/// Red component of the color
+		/// </summary>
+		public byte R { get { return this.GetRgb()[0]; } }
+
+		/// <summary>
+		/// Green component of the color
+		/// </summary>
+		public byte G { get { return this.GetRgb()[1]; } }
+
+		/// <summary>
+		/// Blue component of the color
+		/// </summary>
+		public byte B { get { return this.GetRgb()[2]; } }
+
 		/// <summary>
 		/// Represents the actual stored color.  Either a True Color or an indexed color.
 		/// </summary>
@@ -501,7 +517,7 @@ private static uint getInt24(byte[] array)
 
 		private static ReadOnlySpan<byte> getRGBfromTrueColor(uint color)
 		{
-			return new ReadOnlySpan<byte>(BitConverter.GetBytes(color), 0, 3);
+			return new ReadOnlySpan<byte>(LittleEndianConverter.Instance.GetBytes(color), 0, 3);
 		}
 	}
 }

ACadSharp/IO/DWG/DwgStreamWriters/DwgStreamWriterAC18.cs

@@ -1,4 +1,5 @@
-using System.IO;
+using CSUtilities.Converters;
+using System.IO;
 using System.Text;
 
 namespace ACadSharp.IO.DWG
@@ -11,14 +12,27 @@ public DwgStreamWriterAC18(Stream stream, Encoding encoding) : base(stream, enco
 
 		public override void WriteCmColor(Color value)
 		{
-			//TODO: Finish writer color implementation
-
 			//CMC:
 			//BS: color index(always 0)
 			this.WriteBitShort(0);
 
+			byte[] arr = new byte[4];
+
+			if (value.IsTrueColor)
+			{
+				arr[0] = (byte)(value.R);
+				arr[1] = (byte)(value.G);
+				arr[2] = (byte)(value.B);
+				arr[3] = 0b1100_0010;
+			}
+			else
+			{
+				arr[3] = 0b1100_0011;
+				arr[0] = (byte)value.Index;
+			}
+
 			//BL: RGB value
-			this.WriteBitLong(0);
+			this.WriteBitLong(LittleEndianConverter.Instance.ToInt32(arr));
 
 			//RC: Color Byte
 			this.WriteByte(0);