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