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