Public Class Form1
 
    Dim bmp As New Bitmap("c:\1.png")
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Blanco a Rojo
        ' IMPORTANTE: Utilizar colores ARGB en el primer color
        PictureBox1.BackgroundImage = Fill_Bitmap_Color(bmp, Color.FromArgb(255, 255, 255, 255), Color.Red)
    End Sub
 
    Private Function Fill_Bitmap_Color(ByVal Image As Bitmap, ByVal FromColor As Color, ByVal ToColor As Color)
 
        Dim bmp As New Bitmap(Image)
 
        Dim x As Integer = 0, y As Integer = 0
 
        While x < bmp.Width
            y = 0
            While y < bmp.Height
                If Image.GetPixel(x, y) = FromColor Then bmp.SetPixel(x, y, ToColor)
                Math.Max(Threading.Interlocked.Increment(y), y - 1)
            End While
            Math.Max(Threading.Interlocked.Increment(x), x - 1)
        End While
 
        Return bmp
 
    End Function
 
End Class