Abstract: A symmetric configuration $v_3$ is an incidence structure consisting of $v$ points and $v$ blocks; each block contains three points, each point is in three blocks and no pair of points appears in more than one block. There are two natural colouring problems associated with these objects: a weak colouring is a colouring of the points such that no block is monochromatic, and a strong colouring is a colouring such that no colour appears more than once in a block. In this talk I will explore the history of the weak colouring problem and the related idea of blocking sets in a configuration. I will describe the relationship between the weak and strong chromatic numbers, and mention a number of open problems.
This is joint work with Terry Griggs and Jozef Širáň.
