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)(11,17)(12,19)(13,16)(14,15)(18,24)(20,21)(22,23)(25,26,31,28)(27,32,37,35)(29,38,40,33)(30,34,36,39)(2,3)(6,7)(10,15)(12,17)(16,23)(20,24)(25,27)(26,32)(28,35)(29,30)(31,37)(33,39)(34,38)(36,40) involution — undirected(1,2,5,3)(4,6,8,7)(25,26,31,28)(27,35,37,32)(29,33,40,38)(30,34,36,39)(1,3,5,2)(4,7,8,6)(9,11)(10,12)(13,21)(14,19)(15,17)(16,24)(18,22)(20,23)(25,28,31,26)(27,35,37,32)(29,38,40,33)(30,34,36,39)(1,4,5,8)(2,6,3,7)(9,12)(10,11)(13,20)(14,17)(15,19)(16,18)(21,23)(22,24)(25,29)(26,33)(27,36)(28,38)(30,37)(31,40)(32,34)(35,39)(9,13)(10,16)(11,18)(12,20)(14,22)(15,23)(17,24)(19,21)(25,30,31,36)(26,34,28,39)(27,29,37,40)(32,38,35,33)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.