Those are correct: the Color value is an ARGB value: eight bits each for the Opacity ("A" or the Alpha-channel), Red, Green, and Blue values. If you convert them to Win32 values (which use a RGB space without the Alpha channel) then you get what you see.
If you want to print Color values with opacity, then use the ToArgb method instead:
Color col1 = Color.Red;
Color col2 = Color.Green;
Color col3 = Color.Blue;
Color col4 = Color.White;
Color col5 = Color.Black;
Color col6 = Color.Lime;
Debug.WriteLine($"{col1} = {ColorTranslator.ToWin32(col1):X8}:{(int)col1.ToArgb():X8}");
Debug.WriteLine($"{col2} = {ColorTranslator.ToWin32(col2):X8}:{(int)col2.ToArgb():X8}");
Debug.WriteLine($"{col3} = {ColorTranslator.ToWin32(col3):X8}:{(int)col3.ToArgb():X8}");
Debug.WriteLine($"{col4} = {ColorTranslator.ToWin32(col4):X8}:{(int)col4.ToArgb():X8}");
Debug.WriteLine($"{col5} = {ColorTranslator.ToWin32(col5):X8}:{(int)col5.ToArgb():X8}");
Debug.WriteLine($"{col6} = {ColorTranslator.ToWin32(col6):X8}:{(int)col6.ToArgb():X8}");
Which gives you:
Color [Red] = 000000FF:FFFF0000
Color [Green] = 00008000:FF008000
Color [Blue] = 00FF0000:FF0000FF
Color [White] = 00FFFFFF:FFFFFFFF
Color [Black] = 00000000:FF000000
Color [Lime] = 0000FF00:FF00FF00
Note that Color.Lime is "All green" rather than Color.Green - I have no idea why, other than Lime is kinda too bright for practical use!