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