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