Scintillia marker background coming out a different colour than expected

Question

I'm trying to set Markerbackgrounds for a notepad++ plugin I'm writting so certain lines can be highlighted. The colours are stored as ints which are converted from Color.ToArgb():

int colour = Convert.ToInt32(Color.LightSkyBlue.ToArgb())

From what I understand of the Scintillia documentation it only accepts RGB colours so I use the following function to strip out the Alpha part of the colour. This does set a colour but instead of blue I'm getting orange instead of blue. Is this the right way to set a marker background colour?

       private static void DefineColor(int type, int colour)
    {
        string hexValue = colour.ToString("X");
        hexValue = hexValue.Remove(0, 2);

        //hexValue = "0x" + hexValue

        int decValue = Convert.ToInt32(ColorTranslator.FromHtml(hexValue));
        //int decValue = int.Parse("FF", System.Globalization.NumberStyles.AllowHexSpecifier);

        Win32.SendMessage(PluginBase.nppData._scintillaMainHandle, SciMsg.SCI_MARKERDEFINE, type, (int)SciMsg.SC_MARK_BACKGROUND);
        Win32.SendMessage(PluginBase.nppData._scintillaMainHandle, SciMsg.SCI_MARKERSETBACK, type, decValue);
        Win32.SendMessage(PluginBase.nppData._scintillaMainHandle, SciMsg.SCI_MARKERSETFORE, type, 0);
    }

Answer 1

This strips off any alpha value:

var colorOnly = Color.FromArgb(c.R, c.G, c.B);

This converts the color to a integer value:

int i = c.ToArgb();

Both together:

int i = Color.FromArgb(c.R, c.G, c.B).ToArgb();

But I don't know, if Scintillia uses the same color representation. May it stores the value in BGR instead of RGB format.

int bgr = (c.B * 256 + c.G) * 256 + c.R;