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