When making the argument for why I think two-tone works so well, I often bring up contrast. A two-tone watch is simply interesting to look at. The Root Beer link GMT, while a knockout in solid gold, just loses its extra pop when not in two-tone. Rolex also made its famous Datejust Oysterquartz in two-tone, which is basically retro on link retro. My favorite is the blue dial variant, which has excellent contrast and link handsome looks.