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