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