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