[SDL] Color to B&W

[Lilith Calbridge]

It just goes to show, it's aways something.

I've been working on a presentation using SDL in which I animate the
movement of some logos.  Up to this point in the development I've been
using a pure white background that I blit over the screen surface then
(re)draw all active surfaces because at some point or another some
graphics need to pass over or above other ones so the order of the
drawing is crucial.

Now that the logos are all in position and I have other things to do
with the blank area of the screen I've blitted all the logos to the
background so that I don't have to keep redrawing them.  All I do is
blit the background, when needed, to the screen surface.  However, when
I do this the display shows up in black and white with shades of grey. 
All surfaces have been converted to the same format, 32 bit color, when
the graphic is pulled in from its file.

Can anyone suggest why my display is coming out this way?

TIA,

Lilith