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)(11,18,17,13)(12,20,21,16)(19,23,22,24)(25,26,30,31)(27,32,33,28)(29,37,38,34)(35,36,40,39)(1,3,5,8)(2,6,7,4)(10,15)(12,21)(13,18)(19,22)(25,26,30,31)(27,32,33,28)(29,37,38,34)(35,36,40,39)(1,2)(3,4)(5,7)(6,8)(10,15)(11,17)(16,20)(19,22)(26,31)(27,33)(34,37)(35,40) involution — undirected(1,4)(2,3)(5,6)(7,8)(9,11,14,17)(10,13,15,18)(12,22,21,19)(16,24,20,23)(25,27)(26,32)(28,31)(29,35)(30,33)(34,39)(36,37)(38,40)(1,3)(2,4)(5,8)(6,7)(9,12)(10,16)(11,19)(13,23)(14,21)(15,20)(17,22)(18,24)(25,28,30,32)(26,33,31,27)(29,36,38,39)(34,40,37,35)(1,4)(2,3)(5,6)(7,8)(9,13)(10,17)(11,15)(12,23)(14,18)(16,22)(19,20)(21,24)(25,29,30,38)(26,34,31,37)(27,35,33,40)(28,36,32,39)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.