At the time, when the castle was used for residential purposes, the walls of Rauna Castle were plastered with lime plastering. The layer of plaster over the stones that were slightly projecting above the level of the wall was the thinnest, therefore it was lost first. In other places, the plastering is well preserved. The amount of plastering that has been preserved to date is really impressive. The colour of plaster differed depending on the times, when the castle was inhabited. Initially it was of light colours, later it became grey and brownish, meanwhile, in the 17th century, a plaster of red colour was used. Historical sources contain information that, in one of the premises on the second floor, all archbishops of Riga have been painted on the plastered wall. In Middle Ages, this tradition was practiced at the residences of high level authorities (bishops, archbishops, masters).