In the world of "Demon Slayer: Kimetsu no Yaiba," the swords used by the Demon Slayers are known as Nichirin Blades. These swords are specially crafted from a unique ore and possess special properties that make them effective against demons. Here are the different types of Nichirin Blades mentioned in the series:

1. Black Nichirin Blade: Tanjiro Kamado's sword is a black Nichirin Blade. It changes color when exposed to sunlight, turning black. Tanjiro's blade has a distinct, jagged edge.
2. Scarlet Nichirin Blade: Kanao Tsuyuri wields a Scarlet Nichirin Blade. Its blade has a vibrant red color.
3. Azure Nichirin Blade: Zenitsu Agatsuma's sword is an Azure Nichirin Blade, with a blue hue.
4. White Nichirin Blade: Giyu Tomioka, the Water Hashira, uses a White Nichirin Blade. The color white represents purity.

These are just a few examples of the different types of Nichirin Blades featured in the series. Each Demon Slayer's sword is unique, reflecting their personal traits, breath style, and combat abilities. The color and appearance of a Nichirin Blade can vary among individual Demon Slayers, allowing them to showcase their distinct personalities and fighting styles.