One vertex per element, one color per generator, with an edge from x to x·s.
(2,3)(6,7)(10,15)(11,20)(13,24)(17,30)(19,28)(23,29)(27,32)(34,36) involution — undirected(1,2,5,3)(4,6,8,7)(9,10,16,19,12,15,14,28)(11,21,29,39,20,37,23,35)(13,25,32,31,24,40,27,18)(17,33,34,22,30,26,36,38)(1,3,5,2)(4,6,8,7)(9,11,12,20)(10,17,15,30)(13,26,24,33)(14,29,16,23)(18,35,31,39)(19,36,28,34)(21,25,37,40)(22,27,38,32)(1,4,5,8)(2,6,3,7)(11,20)(17,30)(21,37)(22,38)(23,29)(26,33)(34,36)(35,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.