Assign a Color Value to an Object (.NET)

The following example creates four circles and assigns a different color to each circle using four different methods.

C# Example

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Colors;
 
[CommandMethod("SetObjectColor")]
public static void SetObjectColor()
{
    // Get the current document and database
    Document acDoc = Application.DocumentManager.MdiActiveDocument;
    Database acCurDb = acDoc.Database;

    // Start a transaction
    using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
    {
        // Define an array of colors for the layers
        Color[] acColors = new Color[3];
        acColors[0] = Color.FromColorIndex(ColorMethod.ByAci, 1);
        acColors[1] = Color.FromRgb(23, 54, 232);
        acColors[2] = Color.FromNames("PANTONE Yellow 0131 C",
                                      "PANTONE(R) pastel coated");

        // Open the Block table for read
        BlockTable acBlkTbl;
        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                     OpenMode.ForRead) as BlockTable;

        // Open the Block table record Model space for write
        BlockTableRecord acBlkTblRec;
        acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                        OpenMode.ForWrite) as BlockTableRecord;

        // Create a circle object and assign it the ACI value of 4
        Point3d acPt = new Point3d(0, 3, 0);
        using (Circle acCirc = new Circle())
        {
            acCirc.Center = acPt;
            acCirc.Radius = 1;
            acCirc.ColorIndex = 4;

            acBlkTblRec.AppendEntity(acCirc);
            acTrans.AddNewlyCreatedDBObject(acCirc, true);

            int nCnt = 0;

            while (nCnt < 3)
            {
                // Create a copy of the circle
                Circle acCircCopy;
                acCircCopy = acCirc.Clone() as Circle;

                // Shift the copy along the Y-axis
                acPt = new Point3d(acPt.X, acPt.Y + 3, acPt.Z);
                acCircCopy.Center = acPt;

                // Assign the new color to the circle
                acCircCopy.Color = acColors[nCnt];

                acBlkTblRec.AppendEntity(acCircCopy);
                acTrans.AddNewlyCreatedDBObject(acCircCopy, true);

                nCnt = nCnt + 1;
            }
        }

        // Save the changes and dispose of the transaction
        acTrans.Commit();
    }
}