I am SO EXCITED!!! After some frustration with SU's ribbon selection and matches (and yes, I am a demo!), I came across a website (
www.theribbonretreat.com) with great prices and selection for ribbon and made contact with the owner. I got a copy of her color swatches for their grosgrain ribbon and have been working on matching them to SU's cardstock colors. I was thrilled to match over 35 colors!!!
First, I have to add my disclaimers

:
1) These colors match almost exactly (IN MY OPINION!!), though others not listed would also be close matches to compliment the SU paper
2) There may be SLIGHT shade differences
3) I have included some of the old, retired colors for those who still use them
4) I am in no way affiliated with this company...I just saw good prices and selection and wanted to match them to SU's colors
Here's the list that I came up with (Stampin Up's color will be listed first and then The Ribbon Retreat's matching color):
Whisper White/Confetti White= White
Very Vanilla/Confetti Cream= Lt. Ivory
Basic Black= Black
Going Grey= Millenium Silver
Basic Grey= Flannel Grey
Creamy Caramel= Pecan
Really Rust= Nu Rust or Really Rust
So Saffron= Lemonade
Barely Banana= Wheat
Bravo Burgandy/Cranberry Crisp= Beet
Only Orange= Apricot (a little light)/ Papaya (perfect)/ Orange (a little dark)... any of them look great though
Summer Sun= Gold
YoYo Yellow= Yellow
Pretty In Pink= Rose Pink
Regal Rose= Old Rose/ Pink Passion
Cameo Coral= Dusty Rose
Rose Red/ Purely Pomegranete= Azalea
Marvelous Magenta= Festive Fushia
Real Red= Red
Bravo Burgandy= Maroon
Cool Caribbean= Aquamarine/ Robin's Egg Blue/ Light Blue (all match.. just bring out a different hue)
Bashful Blue= Millennium Blue
Taken with Teal= Sapphire
Tempting Turquiose= Mystic Blue/ Misty Turquiose
Ballet Blue= Capri Blue
Brilliant Blue= Dark Royal
Night of Navy= Lt. Navy
Buckaroo Blue= Williamsburg Blue
Bordering Blue/ Almost Amythest= Wisteria
Lovely Lilac/ Lavender Lace= Tropic Lilac
Orchid Opulence= Dark Orchid
Certainly Celery= Celadon
Mint Melody= Mint
Handsome Hunter= Evergreen
BTW--Most of the ribbon comes in 5 yd. lengths or you can order larger spools from their wholesale website (no tax id # needed). Hope this helps someone else!!-- Jamie