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