Multitone gold has been here since the Edwardian Era and it's still in the contemporary mixed-metal conversation. That's not a trend. That's a design language that keeps coming back because it keeps working.
Elemental Detail
Place an 18kt two-tone piece next to a 14kt equivalent and the color difference is noticeable. The higher gold content in 18kt alloys lends itself to a deeper, more saturated yellow and a brighter, more pronounced white, making the contrast of the two-tones sharper compared to less intense 14kt equivalents.
Visually Speaking
Contrasting gold colors placed deliberately within a 14kt multitone design create visual depth and highlight structural elements that a single-tone piece flattens, which is why multitone pieces tend to read with more complexity at close range.