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