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