Yuzu Kosho is a Japanese paste made with fresh chilis fermented with yuzu and salt. Bon Appetit has called yuzu kosho the, "secret weapon condiment chefs are putting on everything."
The green yuzu kosho uses green chiles. It has a satisfyingly coarse texture that reveals grains of salt, yuzu zest, and green chile pieces that are mashed and mixed together. The green chile imparts a sharper, brighter, grassy flavor and the spiciness is complemented by the tartness of the yuzu. The green kosho is a little bit more common than its red counterpart and is great in tiny amounts on chicken, fish, and on avocado. It can also highlight other fresh herbs, seen in Japanify's pasta recipe or Yuzu Kosho Avocado Toast.
The red yuzu kosho uses red chilis. It is a little bit more smooth and saucy in texture than the green yuzu kosho, even though it still has salt and yuzu peels. The texture is juicier and has an element of tartness you'd get from a fresh tomato. It's a little less spicy than the green yuzu kosho, but has a spice that lingers longer in the mouth. Red kosho is great integrated into a sauce, blended with tarako (cod roe), pasta, or eggs.