Red would complement your collection nicely. Also from the description of your wardrobe I think red would add more excitement - it goes pefectly with both grey and black.
I'm gonna go against the popular votes here because the dark beige just really got to me. I love the color to death and thinking that I could definitely pair it up with so many different outfits. For red, I tend to only wear it with black or white which limits my options. Either way, both are gorgeous colors