Parti-color is somewhat archaic English for "half & half" colors.
Parti-color shows up in dresses, tabards, tunics and the like, starting roughly in the 13th Century especially amongst entertainers such as minstrels and thespians. In the 14th Century, parti-color is popular across all social standings.
Parti-color clothing typically consists of large fields of two colors, with a left-right divide. Colors chosen were usually ones that stood in pretty high-contrast to each other, and so were often bold and bright. So, like in the example in our first "source" link below, the right side might be white, and the left side blue. Accessories would often reverse this pattern. So if the left side of your tabard was blue, the right side of your hose would be blue. Dresses would often follow this design as well, with the skirt reversing the orientation of the bodice. The overall effect of such pairings is that the person has been visually quartered.
More elaborate parti-color might have one of the two fabrics feature stripes or a pattern. Again, you'd have stripes on half the bodice, and the opposite half of the skirt or hose.
Sometimes parti-color hose are worn without the corresponding top, so the color split is contained to just the legs, each of which is a different color.
For an even more outrageous clothing style (that was really only ever popular amongst entertainers) see Motley.
In Animal Breeding
The term parti-color is used to describe two-toned dogs and cats, specifically ones with one or more large spots of a second fur color. Obviously, animals don't come in equally half-and-half or quartered patterns, they have more organic coloration patterns.
Game and Story Use
- Adds a dash of color and verisimilitude to a game set in the late middle ages or renaissance. Having little details like this can help drive home a scene or visual spectacle.
- Parti-color livery might be part of a dress code or heraldry. A group of brigands in red-and-black parti-colored tunics and hose ambush the PCs in the woods. After the fight, the PCs travel to a nearby castle or manor, where the meet the local nobleman. His lordship's colors are red and black, and much of his household staff are wearing the same parti-color as the brigands. Do the PCs lodge a grievance, or slip out of town quickly and quietly?
- Parti-color fashions are garish and cartoony from today's perspective. Only clowns dress like that. So they're a good way to highlight a Fish Out of Temporal Water character, wearing such designs a few hundred years before or after they were popular.
- If a Time Traveler shows up wearing parti-color earlier to far down the timeline, they may be mistaken for an entertainer. Even further off the mark, and they'll be met with laughter or cold stares.
- The goddess Hel likes parti-color so much, she got her skin tattooed to match it. :)