How can I display split color variants in swatch previews?

[RobCupper]

I have some colour variants such as Black/Rust that I would like to display as a split colour circle in the swatch previews on collection pages. Can anyone help> Current it is showing as solid orange colour, I would like it to be half orange, half black if possible. Image attached and site URL is www.slackjawapparel.com - Thanks!