In Chinese calligraphy, the traditional colour of ink is black.
Traditional Chinese ink is made mainly from soot, or lampblack, combined with a binding material such as animal glue. Rather than buying a liquid bottle of ink, a calligrapher traditionally rubs a solid inkstick against an inkstone with a little water. The resulting ink can range from dense, glossy black to lighter gray washes depending on how it is ground and diluted.
Black ink became central to the ideal of Chinese brushwork because variations in pressure, water, and ink concentration allow a single colour to produce many tones. This is especially visible in ink-wash painting, where artists create depth and atmosphere without relying on a full palette.
Gold, blue, and red can appear in Chinese artistic traditions, but they are not the traditional default for calligraphy. Red ink is especially familiar from seals and from teachers’ corrections; coloured inksticks also exist, including cinnabar varieties. Those uses should not be confused with the standard black ink used for writing.