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