Ink and Paint
On this page we can see three different colors of ink The most common ink of the day, iron gall, created the deep black letters. It is made by fermenting oak galls (plant growths found on foliage and twigs that are produced by small oak gall wasps) in water and combining that liquid with vitriol (ferrous sulphate) and gum arabic (hardened sap of the Acacia tree). The galls and vitriol combine to form ferrous tannate which provides the color and the gum arabic thickens the mixture to make it easier to write with.
The red and blue inks were a lot easier to make by comparison, but much more costly, hence their limited use. Red is formed from cinnabar or vermilion, a compound of mercury sulfide, that is ground up and mixed with egg white and gum arabic. The blue is created with azurite, a copper mineral produced by weathering of copper ore deposits, which is ground up and mixed with gum arabic and water.
In all cases, these inks were permanent and as you’ll see in binding, you couldn’t just swap out a page if you made a mistake so calligraphers practiced for years before being allowed to undertake a large or important project.