Convert transparent png in color to single color

Question

I am working with Bitmap C# and wondering how to convert a color png image to only one color. I want all the visible colors in the image to become white. The parts that are transparent should remain transparent. I am going to display these agains a grey background.

Answer 1

The other answers was helpful and got me going, thanks a lot. I couldn't make them work though, not sure why. But I also found out that I wanted to keep the original alpha value of the pixels, rendering the edges smooth. This is what I came up with.

for (int x = 0; x < bitmap.Width; x++)
{
    for (int y = 0; y < bitmap.Height; y++)
    {
        Color bitColor = bitmap.GetPixel(x, y);
        //Sets all the pixels to white but with the original alpha value
        bitmap.SetPixel(x, y, Color.FromArgb(bitColor.A, 255, 255, 255));
    }
}

Here is a screen dump of the result magnified a few times (original on top):
_{(source: codeodyssey.se)}