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