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