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