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