A weak c-colouring of a balanced incomplete block design (BIBD) is a colouring of the points of the design with c colours in such a way that no block of the design has all of its vertices receive the same colour. A BIBD is said to be weakly c-chromatic if c is the smallest number of colours with which the design can be weakly coloured. In this paper we show that for all c ≥ 2 and k ≥ 3 with (c, k) = (2, 3), the obvious necessary conditions for the existence of a (v, k, λ)-BIBD are asymptotically sufficient for the existence of a weakly c-chromatic (v, k, λ)-BIBD.