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