Create image and set its color

public static Bitmap CreateBitmap(int width, int height, Color color)
{
    Bitmap b = new Bitmap(width, -height);
    using (Graphics g = Graphics.FromImage(b))
    {
        g.Clear(color);
    }
    return b;
}

Bitmap bitmap = new Bitmap(100, 100);
for (int i = 0; i < 100; i++)
{
    for (int j = 0; j < 100; j++)
    {
        bitmap.SetPixel(i, j, Color.Blue);
    }
}