heres my code:
Code:
Public Class Form1
    Dim imgImage As Bitmap
    Dim clrOld As Color
    Dim clrNew As Color
    Dim blnChangeColor As Boolean

    Private Sub PictureBox3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PictureBox3.Click
        ColorDialog1.ShowDialog()
        PictureBox3.BackColor = ColorDialog1.Color
        clrNew = ColorDialog1.Color
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        OpenFileDialog1.ShowDialog()
        imgImage = Bitmap.FromFile(OpenFileDialog1.FileName)
        PictureBox1.Image = imgImage
    End Sub

    Private Sub PictureBox1_MouseClick(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseClick
        If e.Button = Windows.Forms.MouseButtons.Left Then
            PictureBox2.BackColor = imgImage.GetPixel(e.X, e.Y)
            clrOld = PictureBox2.BackColor
        End If
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        blnChangeColor = True
        PictureBox1.Invalidate()
    End Sub

    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        Dim x As Integer = 0
        Dim y As Integer = 0
        Dim g As Graphics
        g = PictureBox1.CreateGraphics()

        If blnChangeColor = True Then
            For y = 0 To imgImage.Height - 1
                For x = 0 To imgImage.Width - 1
                    If imgImage.GetPixel(x, y) = clrOld Then
                        imgImage.SetPixel(x, y, clrNew)
                    End If
                Next x
            Next y
            g.DrawImage(imgImage, 0, 0, imgImage.Width, imgImage.Height)
        End If
        PictureBox1.Invalidate()
    End Sub

End Class
i recive these error: "SetPixel is not supported for images with indexed pixel formats."
i don't know why these error
can anyone advice me why?