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