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