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