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