Split complementary color scheme (accented)
We can add the complement to a split-complementary color scheme to achieve additional accenting color. This color scheme is even more vibrant, but a designer can still manage the colors quite easily.
It is recommended to use the complement as the accent color (and not to overuse it), and the two other colors for hilights and additional design elements. We'd better keep all the complementary colors closer to each other to achive the complement feel for all three, comparing to the base color (though not too close to clearly distinguish them). The more distatnt the secondar colors are, the more tension and less maintainable the color scheme is. It's not recommended to add the complement to a triad, as the result is made of 4 colors too distant to communicate together well.
Example
Paletton usage
Within the Paletton application use the Triade (3-color) option with the complementary color switched ON.