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