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