"Today, Melania Trump’s coat was pale blue and Michelle Obama’s was maroon, and that seemed to capture the day: patriotic, yes, but a few shades off."
Two posters have already provided excellent answers. I only add small points for clarity.
There is no one shade of red or any color. There's dark red, bright red, deep red, and they have different names, like 'maroon' which one poster already concisely pointed to the author's meaning. Inauguration Day is considered a "Red, White, and Blue" day, like the 4th of July, where the American flag is prominently displayed. People often wear clothes or hats that show these exact colors on those days to show their patriotism.
What the author is doing is comparing and contrasting two different leaders. Barack Obama, a Democrat, with Donald Trump, a Republican. Not only both parties at odds, but also a President, who on numerous occasions, said there'd never be a Trump President. It was just laughable, as well as his wife, Michelle, who stated all hope for America would be gone with a Trump President. Likewise, Trump made many disparaging comments about Obama's "abysmal leadership" (his word, not mine)...but, the wives of these two men are simply their wives. It's their husbands leaving a political office, and another one taking it - that basically hate each other. Their respective parties also hate each other...but there they are together on stage...like some opposite shades opposing each other.
Michelle Obama is wearing dark red (maroon) - which isn't the shade of red in the stripes of the American Flag. Also, Melanie Trump is wearing blue, but light blue, also not the right shade of blue matching the blue color of the American flag.
The author is simply commenting the off shades of red and blue seem to adequately "capture the day" or represent how off shade and sour the Inauguration of Trump taking over leadership of the country from Obama is by showing in both Michelle and Melanie's off shaded blue and red coats.