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