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