[crusso]

I haven't read all the replies, but it looks like you've gotten plenty of good information. For a raspberry sauce, I also, would probably either use a cornstarch slurry (made with cool raspberry juice or liqour instead of water), or possibly, depending on the amount of sauce you're making, simply let it reduce over a very low flame. This will cause it to not only thicken, but to intensify in flavor as well.

Roux and cream will certainly change the dark color.

Lastly, there are white, blond, brown, and black rouxs, all depending on how long you let them cook. The longer they cook, the darker they get. The longer they cook, the less thickening power they have (so you need to add more of a darker roux than of a white roux), but a nice dark roux will help keep the color of a dark sauce dark.

One last 'lastly'...some folks save their duck fat, or bacon grease, and make a non-traditional roux using other kinds of fat (not just butter, which is classical French). Other people who know they will use this roux for a specific dish may have that, 'smoky bacon roux' or 'curry roux' or duck roux, or anything else your imagination (and ability to utilize leftovers) can bring you.

Good luck!

Chef Carmine J Russo, CCC, CCE