FLOTUS Michelle Obama knows the power of grey. No, seriously she does. First, as you might recall, she donned shimmering grey lavender nails (the color in question was Artistic Nail Design Soak Off Colour Gloss in Vogue) at the 2012 Democratic National Convention. And now, the mom-in-chief turned to the chic shade again for the 2015 State of the Union. This time, she dazzled in a Michael Kors Grey Tweed Origami Jacket with Foldover Collar ($797; back in stock) with the matching Tweed Skirt ($597 the zip-slit rested at the rear). Both pieces are on sale now at Neiman Marcus. Sign up for eBates before you go shopping to receive cash back! Could you imagine if…