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