One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,7)(6,8)(9,10,15,21)(11,22,26,12)(13,31,35,27)(14,36,33,20)(16,24,38,23)(17,28,32,29)(18,39,19,34)(25,30,37,40)(3,8)(5,6)(9,11)(10,16)(12,27)(13,32)(14,37)(15,26)(17,35)(18,40)(19,30)(20,29)(21,38)(22,31)(23,34)(24,39)(25,33)(28,36) involution — undirected(2,5)(3,8)(6,7)(9,12,13,28,33,40,39,16,15,22,35,29,14,30,34,38)(10,17,18,26,36,24,27,25,21,32,19,11,20,23,31,37)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.